@set pxref-help @pxref{help}
@set op-ignore-failed-read @kbd{--ignore-failed-read}
-@set ref-ignore-failed-read @ref{Reading}
-@set xref-ignore-failed-read @xref{Reading}
-@set pxref-ignore-failed-read @pxref{Reading}
+@set ref-ignore-failed-read @ref{create options}
+@set xref-ignore-failed-read @xref{create options}
+@set pxref-ignore-failed-read @pxref{create options}
@set op-ignore-zeros @kbd{--ignore-zeros} (@kbd{-i})
@set ref-ignore-zeros @ref{Reading}
@set xref-version @xref{help}
@set pxref-version @pxref{help}
-@set op-version-control @kbd{--version-control=@var{method}}
-@set ref-version-control @ref{Backup options}
-@set xref-version-control @xref{Backup options}
-@set pxref-version-control @pxref{Backup options}
-
@set op-volno-file @kbd{--volno-file=@var{file-of-number}}
@set ref-volno-file @ref{Using Multiple Tapes}
@set xref-volno-file @xref{Using Multiple Tapes}
@syncodeindex op cp
@ifinfo
-@format
-START-INFO-DIR-ENTRY
+@direntry
* tar: (tar). Making tape (or disk) archives.
-END-INFO-DIR-ENTRY
-@end format
-@end ifinfo
+@end direntry
-@ifinfo
-This file documents GNU @code{tar}, a utility used to store, backup, and
-transport files.
+This file documents @sc{gnu} @command{tar}, which creates and extracts
+files from archives.
+
+Published by the Free Software Foundation,
+59 Temple Place - Suite 330,
+Boston, MA 02111-1307, USA
Copyright 1992, 1994, 1995, 1996, 1997, 1999 Free Software Foundation, Inc.
@setchapternewpage odd
-@shorttitlepage GNU @code{tar}
+@shorttitlepage @sc{gnu} @command{tar}
@titlepage
-@title GNU tar: an archiver tool
+@title @sc{gnu} tar: an archiver tool
@subtitle @value{RENDITION} @value{VERSION}, @value{UPDATED}
@author Melissa Weisshaus, Jay Fenlason,
@author Thomas Bushnell, n/BSG, Amy Gorin
by the Foundation.
@end titlepage
-@ifinfo
+@ifnottex
+@node Top
+@top Tar
-This file documents GNU @code{tar}, which is a utility used to store,
-backup, and transport files. @code{tar} is a tape (or disk) archiver.
-This manual documents the release @value{VERSION}.
+@cindex file archival
+@cindex archiving files
-@end ifinfo
+@sc{gnu} @command{tar} creates and extracts files from archives.
-@node Top, Introduction, (dir), (dir)
+This manual documents version @value{VERSION} of @sc{gnu} @command{tar}.
+
+The first part of this master menu lists the major nodes in this Info
+document. The rest of the menu lists all the lower level nodes.
+@end ifnottex
@menu
* Introduction::
* Media::
* Index::
+@detailmenu
+
--- The Detailed Node Listing ---
Introduction
* Book Contents:: What this Book Contains
* Definitions:: Some Definitions
-* What tar Does:: What @code{tar} Does
-* Naming tar Archives:: How @code{tar} Archives are Named
+* What tar Does:: What @command{tar} Does
+* Naming tar Archives:: How @command{tar} Archives are Named
* posix compliance::
-* Authors:: GNU @code{tar} Authors
+* Authors:: @sc{gnu} @command{tar} Authors
* Reports:: Reporting bugs or suggestions
-Tutorial Introduction to @code{tar}
+Tutorial Introduction to @command{tar}
* assumptions::
* stylistic conventions::
-* basic tar options:: Basic @code{tar} Operations and Options
+* basic tar options:: Basic @command{tar} Operations and Options
* frequent operations::
* Two Frequent Options::
* create:: How to Create Archives
* extract dir::
* failing commands::
-Invoking GNU @code{tar}
+Invoking @sc{gnu} @command{tar}
* Synopsis::
* using tar options::
* Old Options:: Old Option Style
* Mixing:: Mixing Option Styles
-All @code{tar} Options
+All @command{tar} Options
* Operation Summary::
* Option Summary::
* Short Option Summary::
-GNU @code{tar} Operations
+@sc{gnu} @command{tar} Operations
* Basic tar::
* Advanced tar::
+* create options::
* extract options::
* backup::
* Applications::
* looking ahead::
-Advanced GNU @code{tar} Operations
+Advanced @sc{gnu} @command{tar} Operations
* Operations::
* current state::
* how to update::
+Options used by @code{--create}
+
+* Ignore Failed Read::
+
Options Used by @code{--extract}
* Reading:: Options to Help Read Archives
-* Writing:: Changing How @code{tar} Writes Files
+* Writing:: Changing How @command{tar} Writes Files
* Scarce:: Coping with Scarce Resources
Options to Help Read Archives
* read full records::
* Ignore Zeros::
-* Ignore Failed Read::
-Changing How @code{tar} Writes Files
+Changing How @command{tar} Writes Files
* Prevention Overwriting::
* Keep Old Files::
Performing Backups and Restoring Files
-* Full Dumps:: Using @code{tar} to Perform Full Dumps
-* Inc Dumps:: Using @code{tar} to Perform Incremental Dumps
+* Full Dumps:: Using @command{tar} to Perform Full Dumps
+* Inc Dumps:: Using @command{tar} to Perform Incremental Dumps
* incremental and listed-incremental:: The Incremental Options
* Backup Levels:: Levels of Backups
* Backup Parameters:: Setting Parameters for Backups and Restoration
* backup-specs example:: An Example Text of @file{Backup-specs}
* Script Syntax:: Syntax for @file{Backup-specs}
-Choosing Files and Names for @code{tar}
+Choosing Files and Names for @command{tar}
* file:: Choosing the Archive's Name
* Selecting Archive Members::
* General date syntax:: Common rules.
* Calendar date item:: 19 Dec 1994.
* Time of day item:: 9:20pm.
-* Time zone item:: EST, GMT, UTC, ...
+* Time zone item:: @sc{est}, @sc{gmt}, @sc{utc}, ...
* Day of week item:: Monday and others.
* Relative item in date strings:: next tuesday, 2 years ago.
* Pure numbers in date strings:: 19931219, 1440.
Controlling the Archive Format
-* Portability:: Making @code{tar} Archives More Portable
+* Portability:: Making @command{tar} Archives More Portable
* Compression:: Using Less Space through Compression
* Attributes:: Handling File Attributes
* Standard:: The Standard Format
-* Extensions:: GNU Extensions to the Archive Format
-* cpio:: Comparison of @code{tar} and @code{cpio}
+* Extensions:: @sc{gnu} Extensions to the Archive Format
+* cpio:: Comparison of @command{tar} and @command{cpio}
-Making @code{tar} Archives More Portable
+Making @command{tar} Archives More Portable
* Portable Names:: Portable Names
* dereference:: Symbolic Links
* old:: Old V7 Archives
-* posix:: POSIX archives
+* posix:: @sc{posix} archives
* Checksumming:: Checksumming Problems
+* Large or Negative Values:: Large files, negative time stamps, etc.
Using Less Space through Compression
Many Archives on One Tape
* Tape Positioning:: Tape Positions and Tape Marks
-* mt:: The @code{mt} Utility
+* mt:: The @command{mt} Utility
Using Multiple Tapes
* Multi-Volume Archives:: Archives Longer than One Tape or Disk
* Tape Files:: Tape Files
+@end detailmenu
@end menu
-@node Introduction, Tutorial, Top, Top
+@node Introduction
@chapter Introduction
-Welcome to the GNU @code{tar} manual. GNU @code{tar} is used to create
-and manipulate files (@dfn{archives}) which are actually collections of
+Welcome to the @sc{gnu} @command{tar} manual. @sc{gnu} @command{tar} creates
+and manipulates (@dfn{archives}) which are actually collections of
many other files; the program provides users with an organized and
systematic method for controlling a large amount of data.
@menu
* Book Contents:: What this Book Contains
* Definitions:: Some Definitions
-* What tar Does:: What @code{tar} Does
-* Naming tar Archives:: How @code{tar} Archives are Named
+* What tar Does:: What @command{tar} Does
+* Naming tar Archives:: How @command{tar} Archives are Named
* posix compliance::
-* Authors:: GNU @code{tar} Authors
+* Authors:: @sc{gnu} @command{tar} Authors
* Reports:: Reporting bugs or suggestions
@end menu
-@node Book Contents, Definitions, Introduction, Introduction
-@ifinfo
-@heading What this Book Contains
-@end ifinfo
+@node Book Contents
+@section What this Book Contains
The first part of this chapter introduces you to various terms that will
-recur throughout the book. It also tells you who has worked on GNU
-@code{tar} and its documentation, and where you should send bug reports
+recur throughout the book. It also tells you who has worked on @sc{gnu}
+@command{tar} and its documentation, and where you should send bug reports
or comments.
The second chapter is a tutorial (@pxref{Tutorial}) which provides a
-gentle introduction for people who are new to using @code{tar}. It is
+gentle introduction for people who are new to using @command{tar}. It is
meant to be self contained, not requiring any reading from subsequent
chapters to make sense. It moves from topic to topic in a logical,
progressive order, building on information already explained.
Although the tutorial is paced and structured to allow beginners to
-learn how to use @code{tar}, it is not intended solely for beginners.
+learn how to use @command{tar}, it is not intended solely for beginners.
The tutorial explains how to use the three most frequently used
operations (@samp{create}, @samp{list}, and @samp{extract}) as well as
two frequently used options (@samp{file} and @samp{verbose}). The other
concepts of using a Unix-type operating system; @pxref{Tutorial}.)
The third chapter presents the remaining five operations, and
-information about using @code{tar} options and option syntax.
+information about using @command{tar} options and option syntax.
-@FIXME{this sounds more like a GNU Project Manuals Concept [tm] more
+@FIXME{this sounds more like a @sc{gnu} Project Manuals Concept [tm] more
than the reality. should think about whether this makes sense to say
here, or not.} The other chapters are meant to be used as a
reference. Each chapter presents everything that needs to be said
about a specific topic.
One of the chapters (@pxref{Date input formats}) exists in its entirety
-in other GNU manuals, and is mostly self-contained. In addition, one
+in other @sc{gnu} manuals, and is mostly self-contained. In addition, one
section of this manual (@pxref{Standard}) contains a big quote which is
-taken directly from @code{tar} sources.
+taken directly from @command{tar} sources.
In general, we give both the long and short (abbreviated) option names
at least once in each section where the relevant option is covered, so
options have no short versions, and the relevant sections will
indicate this.)
-@node Definitions, What tar Does, Book Contents, Introduction
+@node Definitions
@section Some Definitions
@cindex archive
@cindex tar archive
-The @code{tar} program is used to create and manipulate @code{tar}
+The @command{tar} program is used to create and manipulate @command{tar}
archives. An @dfn{archive} is a single file which contains the contents
of many files, while still identifying the names of the files, their
owner(s), and so forth. (In addition, archives record access
permissions, user and group, size in bytes, and last modification time.
Some archives also record the file names in each archived directory, as
-well as other file and directory information.) You can use @code{tar}
+well as other file and directory information.) You can use @command{tar}
to @dfn{create} a new archive in a specified directory.
@cindex member
@cindex member name
The files inside an archive are called @dfn{members}. Within this
manual, we use the term @dfn{file} to refer only to files accessible in
-the normal ways (by @code{ls}, @code{cat}, and so forth), and the term
+the normal ways (by @command{ls}, @command{cat}, and so forth), and the term
@dfn{member} to refer only to the members of an archive. Similarly, a
@dfn{file name} is the name of a file, as it resides in the filesystem,
and a @dfn{member name} is the name of an archive member within the
the archive. You may also @dfn{list} the members in a given archive
(this is often thought of as ``printing'' them to the standard output,
or the command line), or @dfn{append} members to a pre-existing archive.
-All of these operations can be performed using @code{tar}.
+All of these operations can be performed using @command{tar}.
-@node What tar Does, Naming tar Archives, Definitions, Introduction
-@section What @code{tar} Does
+@node What tar Does
+@section What @command{tar} Does
@cindex tar
-The @code{tar} program provides the ability to create @code{tar}
+The @command{tar} program provides the ability to create @command{tar}
archives, as well as various other kinds of manipulation. For example,
-you can use @code{tar} on previously created archives to extract files,
+you can use @command{tar} on previously created archives to extract files,
to store additional files, or to update or list files which were already
stored.
-Initially, @code{tar} archives were used to store files conveniently on
-magnetic tape. The name @samp{tar} comes from this use; it stands for
-@code{t}ape @code{ar}chiver. Despite the utility's name, @code{tar} can
+Initially, @command{tar} archives were used to store files conveniently on
+magnetic tape. The name @command{tar} comes from this use; it stands for
+@code{t}ape @code{ar}chiver. Despite the utility's name, @command{tar} can
direct its output to available devices, files, or other programs (using
-pipes). @code{tar} may even access remote devices or files (as archives).
+pipes). @command{tar} may even access remote devices or files (as archives).
@FIXME{the following table entries need a bit of work..}
-You can use @code{tar} archives in many ways. We want to stress a few
+You can use @command{tar} archives in many ways. We want to stress a few
of them: storage, backup, and transportation.
@table @asis
@item Storage
-Often, @code{tar} archives are used to store related files for
-convenient file transfer over a network. For example, the GNU Project
-distributes its software bundled into @code{tar} archives, so that
+Often, @command{tar} archives are used to store related files for
+convenient file transfer over a network. For example, the @sc{gnu} Project
+distributes its software bundled into @command{tar} archives, so that
all the files relating to a particular program (or set of related
programs) can be transferred as a single unit.
A magnetic tape can store several files in sequence. However, the tape
has no names for these files; it only knows their relative position on
the tape. One way to store several files on one tape and retain their
-names is by creating a @code{tar} archive. Even when the basic transfer
+names is by creating a @command{tar} archive. Even when the basic transfer
mechanism can keep track of names, as FTP can, the nuisance of handling
-multiple files, directories, and multiple links makes @code{tar}
+multiple files, directories, and multiple links makes @command{tar}
archives useful.
Archive files are also used for long-term storage. You can think of
this as transportation from the present into the future. (It is a
science-fiction idiom that you can move through time as well as in
-space; the idea here is that @code{tar} can be used to move archives in
+space; the idea here is that @command{tar} can be used to move archives in
all dimensions, even time!)
@item Backup
-Because the archive created by @code{tar} is capable of preserving file
-information and directory structure, @code{tar} is commonly used for
+Because the archive created by @command{tar} is capable of preserving file
+information and directory structure, @command{tar} is commonly used for
performing full and incremental backups of disks. A backup puts a
collection of files (possibly pertaining to many users and
projects) together on a disk or a tape. This guards against accidental
-destruction of the information in those files. GNU @code{tar} has
+destruction of the information in those files. @sc{gnu} @command{tar} has
special features that allow it to be used to make incremental and full
dumps of all the files in a filesystem.
files from one system to another.
@end table
-@node Naming tar Archives, posix compliance, What tar Does, Introduction
-@section How @code{tar} Archives are Named
+@node Naming tar Archives
+@section How @command{tar} Archives are Named
-Conventionally, @code{tar} archives are given names ending with
-@samp{.tar}. This is not necessary for @code{tar} to operate properly,
+Conventionally, @command{tar} archives are given names ending with
+@samp{.tar}. This is not necessary for @command{tar} to operate properly,
but this manual follows that convention in order to accustom readers to
it and to make examples more clear.
@cindex tar file
@cindex entry
@cindex tar entry
-Often, people refer to @code{tar} archives as ``@code{tar} files,'' and
+Often, people refer to @command{tar} archives as ``@command{tar} files,'' and
archive members as ``files'' or ``entries''. For people familiar with
-the operation of @code{tar}, this causes no difficulty. However, in
+the operation of @command{tar}, this causes no difficulty. However, in
this manual, we consistently refer to ``archives'' and ``archive
-members'' to make learning to use @code{tar} easier for novice users.
+members'' to make learning to use @command{tar} easier for novice users.
-@node posix compliance, Authors, Naming tar Archives, Introduction
-@section POSIX Compliance
+@node posix compliance
+@section @sc{posix} Compliance
@noindent
@FIXME{must ask franc,ois about this. dan hagerty thinks this might
We make some of our recommendations throughout this book for one
reason in addition to what we think of as ``good sense''. The main
additional reason for a recommendation is to be compliant with the
-POSIX standards. If you set the shell environment variable
-@code{POSIXLY_CORRECT}, GNU @code{tar} will force you to adhere to
+@sc{posix} standards. If you set the shell environment variable
+@env{POSIXLY_CORRECT}, @sc{gnu} @command{tar} will force you to adhere to
these standards. Therefore, if this variable is set and you violate
-one of the POSIX standards in the way you phrase a command, for
-example, GNU @code{tar} will not allow the command and will signal an
+one of the @sc{posix} standards in the way you phrase a command, for
+example, @sc{gnu} @command{tar} will not allow the command and will signal an
error message. You would then have to reorder the options or rephrase
-the command to comply with the POSIX standards.
+the command to comply with the @sc{posix} standards.
There is a chance in the future that, if you set this environment
-variable, your archives will be forced to comply with POSIX standards,
-also. No GNU @code{tar} extensions will be allowed.
+variable, your archives will be forced to comply with @sc{posix} standards,
+also. No @sc{gnu} @command{tar} extensions will be allowed.
-@node Authors, Reports, posix compliance, Introduction
-@section GNU @code{tar} Authors
+@node Authors
+@section @sc{gnu} @command{tar} Authors
-GNU @code{tar} was originally written by John Gilmore, and modified by
-many people. The GNU enhancements were written by Jay Fenlason, then
+@sc{gnu} @command{tar} was originally written by John Gilmore, and modified by
+many people. The @sc{gnu} enhancements were written by Jay Fenlason, then
Joy Kendall, and the whole package has been further maintained by
Thomas Bushnell, n/BSG, and finally Fran@,{c}ois Pinard, with
the help of numerous and kind users.
-We wish to stress that @code{tar} is a collective work, and owes much to
+We wish to stress that @command{tar} is a collective work, and owes much to
all those people who reported problems, offered solutions and other
insights, or shared their thoughts and suggestions. An impressive, yet
partial list of those contributors can be found in the @file{THANKS}
-file from the GNU @code{tar} distribution.
+file from the @sc{gnu} @command{tar} distribution.
@FIXME{i want all of these names mentioned, Absolutely. BUT, i'm not
sure i want to spell out the history in this detail, at least not for
@FIXME{History is more important, and surely more interesting, than
actual names. Quoting names without history would be meaningless. FP}
-Jay Fenlason put together a draft of a GNU @code{tar} manual,
+Jay Fenlason put together a draft of a @sc{gnu} @command{tar} manual,
borrowing notes from the original man page from John Gilmore. This
was withdrawn in version
1.11. Thomas Bushnell, n/BSG and Amy Gorin worked on a tutorial and
-manual for GNU @code{tar}. Fran@,{c}ois Pinard put version 1.11.8
+manual for @sc{gnu} @command{tar}. Fran@,{c}ois Pinard put version 1.11.8
of the manual together by taking information from all these sources
and merging them. Melissa Weisshaus finally edited and redesigned the
book to create version 1.12. @FIXME{update version number as
For version 1.12, Daniel Hagerty contributed a great deal of technical
consulting. In particular, he is the primary author of @ref{Backups}.
-@node Reports, , Authors, Introduction
+@node Reports
@section Reporting bugs or suggestions
@cindex bug reports
If you find problems or have suggestions about this program or manual,
please report them to @file{bug-tar@@gnu.org}.
-@node Tutorial, tar invocation, Introduction, Top
-@chapter Tutorial Introduction to @code{tar}
+@node Tutorial
+@chapter Tutorial Introduction to @command{tar}
-This chapter guides you through some basic examples of three @code{tar}
+This chapter guides you through some basic examples of three @command{tar}
operations: @samp{--create}, @samp{--list}, and @samp{--extract}. If
-you already know how to use some other version of @code{tar}, then you
+you already know how to use some other version of @command{tar}, then you
may not need to read this chapter. This chapter omits most complicated
-details about how @code{tar} works.
+details about how @command{tar} works.
@menu
* assumptions::
* stylistic conventions::
-* basic tar options:: Basic @code{tar} Operations and Options
+* basic tar options:: Basic @command{tar} Operations and Options
* frequent operations::
* Two Frequent Options::
* create:: How to Create Archives
* going further::
@end menu
-@node assumptions, stylistic conventions, Tutorial, Tutorial
-@ifinfo
-@heading Assumptions this Tutorial Makes
-@end ifinfo
+@node assumptions
+@section Assumptions this Tutorial Makes
-This chapter is paced to allow beginners to learn about @code{tar}
+This chapter is paced to allow beginners to learn about @command{tar}
slowly. At the same time, we will try to cover all the basic aspects of
these three operations. In order to accomplish both of these tasks, we
have made certain assumptions about your knowledge before reading this
@item
This manual assumes that you are working from your own home directory
(unless we state otherwise). In this tutorial, you will create a
-directory to practice @code{tar} commands in. When we show path names,
+directory to practice @command{tar} commands in. When we show path names,
we will assume that those paths are relative to your home directory.
For example, my home directory path is @file{/home/fsf/melissa}. All of
my examples are in a subdirectory of the directory named by that path
Additionally, working with tapes is much more complicated than working
with hard disks. For these reasons, the tutorial does not cover working
with tape drives. @xref{Media}, for complete information on using
-@code{tar} archives with tape drives.
+@command{tar} archives with tape drives.
@FIXME{this is a cop out. need to add some simple tape drive info.}
@end itemize
-@node stylistic conventions, basic tar options, assumptions, Tutorial
-@ifinfo
-@heading Stylistic Conventions
-@end ifinfo
+@node stylistic conventions
+@section Stylistic Conventions
In the examples, @samp{$} represents a typical shell prompt. It
precedes lines you should type; to make this more clear, those lines are
@FIXME{how often do we use smallexample?}
-@node basic tar options, frequent operations, stylistic conventions, Tutorial
-@section Basic @code{tar} Operations and Options
+@node basic tar options
+@section Basic @command{tar} Operations and Options
-@code{tar} can take a wide variety of arguments which specify and define
+@command{tar} can take a wide variety of arguments which specify and define
the actions it will have on the particular set of files or the archive.
-The main types of arguments to @code{tar} fall into one of two classes:
+The main types of arguments to @command{tar} fall into one of two classes:
operations, and options.
Some arguments fall into a class called @dfn{operations}; exactly one of
-these is both allowed and required for any instance of using @code{tar};
+these is both allowed and required for any instance of using @command{tar};
you may @emph{not} specify more than one. People sometimes speak of
@dfn{operating modes}. You are in a particular operating mode when you
have specified the operation which specifies it; there are eight
The other arguments fall into the class known as @dfn{options}. You are
not required to specify any options, and you are allowed to specify more
-than one at a time (depending on the way you are using @code{tar} at
+than one at a time (depending on the way you are using @command{tar} at
that time). Some options are used so frequently, and are so useful for
helping you type commands more carefully that they are effectively
``required''. We will discuss them in this chapter.
-You can write most of the @code{tar} operations and options in any of
+You can write most of the @command{tar} operations and options in any of
three forms: long (mnemonic) form, short form, and old style. Some of
the operations and options have no short or ``old'' forms; however, the
operations and options which we will cover in this tutorial have
corresponding abbreviations. @FIXME{make sure this is still the case,
at the end}We will indicate those abbreviations appropriately to get
you used to seeing them. (Note that the ``old style'' option forms
-exist in GNU @code{tar} for compatibility with Unix @code{tar}. We
+exist in @sc{gnu} @command{tar} for compatibility with Unix @command{tar}. We
present a full discussion of this way of writing options and operations
appears in @ref{Old Options}, and we discuss the other two styles of
writing options in @ref{Mnemonic Options} and @ref{Short Options}.)
In the examples and in the text of this tutorial, we usually use the
long forms of operations and options; but the ``short'' forms produce
-the same result and can make typing long @code{tar} commands easier.
+the same result and can make typing long @command{tar} commands easier.
For example, instead of typing
@example
The term, ``option'', can be confusing at times, since ``operations''
are often lumped in with the actual, @emph{optional} ``options'' in certain
general class statements. For example, we just talked about ``short and
-long forms of options and operations''. However, experienced @code{tar}
+long forms of options and operations''. However, experienced @command{tar}
users often refer to these by shorthand terms such as, ``short and long
options''. This term assumes that the ``operations'' are included, also.
Context will help you determine which definition of ``options'' to use.
Similarly, the term ``command'' can be confusing, as it is often used in
-two different ways. People sometimes refer to @code{tar} ``commands''.
-A @code{tar} @dfn{command} is the entire command line of user input
-which tells @code{tar} what to do --- including the operation, options,
+two different ways. People sometimes refer to @command{tar} ``commands''.
+A @command{tar} @dfn{command} is the entire command line of user input
+which tells @command{tar} what to do --- including the operation, options,
and any arguments (file names, pipes, other commands, etc). However,
-you will also sometimes hear the term ``the @code{tar} command''. When
+you will also sometimes hear the term ``the @command{tar} command''. When
the word ``command'' is used specifically like this, a person is usually
-referring to the @code{tar} @emph{operation}, not the whole line.
+referring to the @command{tar} @emph{operation}, not the whole line.
Again, use context to figure out which of the meanings the speaker
intends.
-@node frequent operations, Two Frequent Options, basic tar options, Tutorial
+@node frequent operations
@section The Three Most Frequently Used Operations
Here are the three most frequently used operations (both short and long
@table @kbd
@item --create
@itemx -c
-Create a new @code{tar} archive.
+Create a new @command{tar} archive.
@item --list
@itemx -t
List the contents of an archive.
Extract one or more members from an archive.
@end table
-@node Two Frequent Options, create, frequent operations, Tutorial
+@node Two Frequent Options
@section Two Frequently Used Options
-To understand how to run @code{tar} in the three operating modes listed
+To understand how to run @command{tar} in the three operating modes listed
previously, you also need to understand how to use two of the options to
-@code{tar}: @samp{--file} (which takes an archive file as an argument)
+@command{tar}: @samp{--file} (which takes an archive file as an argument)
and @samp{--verbose}. (You are usually not @emph{required} to specify
-either of these options when you run @code{tar}, but they can be very
+either of these options when you run @command{tar}, but they can be very
useful in making things more clear and helping you avoid errors.)
@menu
* help tutorial::
@end menu
-@node file tutorial, verbose tutorial, Two Frequent Options, Two Frequent Options
+@node file tutorial
@unnumberedsubsec The @samp{--file} Option
@table @kbd
@end table
You can specify an argument for the @value{op-file} option whenever you
-use @code{tar}; this option determines the name of the archive file
-that @code{tar} will work on.
+use @command{tar}; this option determines the name of the archive file
+that @command{tar} will work on.
-If you don't specify this argument, then @code{tar} will use a
+If you don't specify this argument, then @command{tar} will use a
default, usually some physical tape drive attached to your machine.
If there is no tape drive attached, or the default is not meaningful,
-then @code{tar} will print an error message. The error message might
+then @command{tar} will print an error message. The error message might
look roughly like one of the following:
@example
@noindent
To avoid confusion, we recommend that you always specify an archive file
-name by using @value{op-file} when writing your @code{tar} commands.
+name by using @value{op-file} when writing your @command{tar} commands.
For more information on using the @value{op-file} option, see
@ref{file}.
-@node verbose tutorial, help tutorial, file tutorial, Two Frequent Options
+@node verbose tutorial
@unnumberedsubsec The @samp{--verbose} Option
@table @kbd
@item --verbose
@itemx -v
-Show the files being worked on as @code{tar} is running.
+Show the files being worked on as @command{tar} is running.
@end table
@value{op-verbose} shows details about the results of running
-@code{tar}. This can be especially useful when the results might not be
-obvious. For example, if you want to see the progress of @code{tar} as
+@command{tar}. This can be especially useful when the results might not be
+obvious. For example, if you want to see the progress of @command{tar} as
it writes files into the archive, you can use the @samp{--verbose}
option. In the beginning, you may find it useful to use
@samp{--verbose} at all times; when you are more accustomed to
-@code{tar}, you will likely want to use it at certain times but not at
+@command{tar}, you will likely want to use it at certain times but not at
others. We will use @samp{--verbose} at times to help make something
clear, and we will give many examples both using and not using
@samp{--verbose} to show the differences.
Later in the tutorial, we will give examples using @w{@samp{--verbose
--verbose}}.
-@node help tutorial, , verbose tutorial, Two Frequent Options
+@node help tutorial
@unnumberedsubsec Getting Help: Using the @code{--help} Option
@table @kbd
@item --help
-The @samp{--help} option to @code{tar} prints out a very brief list of
+The @samp{--help} option to @command{tar} prints out a very brief list of
all operations and option available for the current version of
-@code{tar} available on your system.
+@command{tar} available on your system.
@end table
-@node create, list, Two Frequent Options, Tutorial
+@node create
@section How to Create Archives
@UNREVISED
-One of the basic operations of @code{tar} is @value{op-create}, which
-you use to create a @code{tar} archive. We will explain
+One of the basic operations of @command{tar} is @value{op-create}, which
+you use to create a @command{tar} archive. We will explain
@samp{--create} first because, in order to learn about the other
operations, you will find it useful to have an archive available to
practice on.
forms. In the rest of the tutorial, and in the examples in the next
chapter, we will proceed at a slightly quicker pace. This section
moves more slowly to allow beginning users to understand how
-@code{tar} works.
+@command{tar} works.
@menu
* prepare for examples::
* create dir::
@end menu
-@node prepare for examples, Creating the archive, create, create
+@node prepare for examples
@subsection Preparing a Practice Directory for Examples
To follow along with this and future examples, create a new directory
and be of different lengths. Our examples assume that @file{practice}
is a subdirectory of your home directory.
-Now @code{cd} to the directory named @file{practice}; @file{practice}
+Now @command{cd} to the directory named @file{practice}; @file{practice}
is now your @dfn{working directory}. (@emph{Please note}: Although
the full path name of this directory is
@file{/@var{homedir}/practice}, in our examples we will refer to
this directory as @file{practice}; the @var{homedir} is presumed.
In general, you should check that the files to be archived exist where
-you think they do (in the working directory) by running @code{ls}.
+you think they do (in the working directory) by running @command{ls}.
Because you just created the directory and the files and have changed to
that directory, you probably don't need to do that this time.
It is very important to make sure there isn't already a file in the
working directory with the archive name you intend to use (in this case,
@samp{collection.tar}), or that you don't care about its contents.
-Whenever you use @samp{create}, @code{tar} will erase the current
-contents of the file named by @value{op-file} if it exists. @code{tar}
+Whenever you use @samp{create}, @command{tar} will erase the current
+contents of the file named by @value{op-file} if it exists. @command{tar}
will not tell you if you are about to overwrite a file unless you
specify an option which does this. @FIXME{xref to the node for
--backup!}To add files to an existing archive, you need to use a
different option, such as @value{op-append}; see @ref{append} for
information on how to do this.
-@node Creating the archive, create verbose, prepare for examples, create
+@node Creating the archive
@subsection Creating the Archive
To place the files @file{blues}, @file{folk}, and @file{jazz} into an
However, you can see that this order is harder to understand; this is
why we will list the arguments in the order that makes the commands
easiest to understand (and we encourage you to do the same when you use
-@code{tar}, to avoid errors).
+@command{tar}, to avoid errors).
Note that the part of the command which says,
@w{@kbd{--file=collection.tar}} is considered to be @emph{one} argument.
@FIXME{xref to definitions?}
When you create an archive, you @emph{must} specify which files you want
-placed in the archive. If you do not specify any archive members, GNU
-@code{tar} will complain.
+placed in the archive. If you do not specify any archive members, @sc{gnu}
+@command{tar} will complain.
If you now list the contents of the working directory (@kbd{ls}), you will
find the archive file listed as well as the files you saw previously:
Creating the archive @samp{collection.tar} did not destroy the copies of
the files in the directory.
-Keep in mind that if you don't indicate an operation, @code{tar} will not
-run and will prompt you for one. If you don't name any files, @code{tar}
+Keep in mind that if you don't indicate an operation, @command{tar} will not
+run and will prompt you for one. If you don't name any files, @command{tar}
will complain. You must have write access to the working directory,
or else you will not be able to create an archive in that directory.
an existing archive; it will delete the archive and write a new one.
Use @value{op-append} instead. @xref{append}.
-@node create verbose, short create, Creating the archive, create
+@node create verbose
@subsection Running @samp{--create} with @samp{--verbose}
If you include the @value{op-verbose} option on the command line,
-@code{tar} will list the files it is acting on as it is working. In
+@command{tar} will list the files it is acting on as it is working. In
verbose mode, the @code{create} example above would appear as:
@example
@end example
This example is just like the example we showed which did not use
-@samp{--verbose}, except that @code{tar} generated the remaining lines
+@samp{--verbose}, except that @command{tar} generated the remaining lines
@iftex
(note the different font styles).
@end iftex
@end ifinfo
In the rest of the examples in this chapter, we will frequently use
-@code{verbose} mode so we can show actions or @code{tar} responses that
+@code{verbose} mode so we can show actions or @command{tar} responses that
you would otherwise not see, and which are important for you to
understand.
-@node short create, create dir, create verbose, create
+@node short create
@subsection Short Forms with @samp{create}
As we said before, the @value{op-create} operation is one of the most
-basic uses of @code{tar}, and you will use it countless times.
+basic uses of @command{tar}, and you will use it countless times.
Eventually, you will probably want to use abbreviated (or ``short'')
forms of options. A full discussion of the three different forms that
options can take appears in @ref{Styles}; for now, here is what the
@end example
@noindent
-In this case, @code{tar} will make an archive file called @file{v},
+In this case, @command{tar} will make an archive file called @file{v},
containing the files @file{blues}, @file{folk}, and @file{jazz}, because
the @samp{v} is the closest ``file name'' to the @samp{-f} option, and
-is thus taken to be the chosen archive file name. @code{tar} will try
+is thus taken to be the chosen archive file name. @command{tar} will try
to add a file called @file{collection.tar} to the @file{v} archive file;
-if the file @file{collection.tar} did not already exist, @code{tar} will
+if the file @file{collection.tar} did not already exist, @command{tar} will
report an error indicating that this file does not exist. If the file
@file{collection.tar} does already exist (e.g., from a previous command
-you may have run), then @code{tar} will add this file to the archive.
-Because the @samp{-v} option did not get registered, @code{tar} will not
+you may have run), then @command{tar} will add this file to the archive.
+Because the @samp{-v} option did not get registered, @command{tar} will not
run under @samp{verbose} mode, and will not report its progress.
The end result is that you may be quite confused about what happened,
especially when using short option forms. Not having the option name
written out mnemonically can affect how well you remember which option
does what, and therefore where different names have to be placed.
-(Placing options in an unusual order can also cause @code{tar} to
-report an error if you have set the shell environment variable,
-@code{POSIXLY_CORRECT}; @pxref{posix compliance} for more information
+(Placing options in an unusual order can also cause @command{tar} to
+report an error if you have set the shell environment variable
+@env{POSIXLY_CORRECT}; @pxref{posix compliance} for more information
on this.)
-@node create dir, , short create, create
+@node create dir
@subsection Archiving Directories
@cindex Archiving Directories
@cindex Directories, Archiving
You can archive a directory by specifying its directory name as a
-file name argument to @code{tar}. The files in the directory will be
+file name argument to @command{tar}. The files in the directory will be
archived relative to the working directory, and the directory will be
re-created along with its contents when the archive is extracted.
@end example
@noindent
-@code{tar} should output:
+@command{tar} should output:
@example
practice/
Note that the archive thus created is not in the subdirectory
@file{practice}, but rather in the current working directory---the
-directory from which @code{tar} was invoked. Before trying to archive a
+directory from which @command{tar} was invoked. Before trying to archive a
directory from its superior directory, you should make sure you have
write access to the superior directory itself, not only the directory
-you are trying archive with @code{tar}. For example, you will probably
+you are trying archive with @command{tar}. For example, you will probably
not be able to store your home directory in an archive by invoking
-@code{tar} from the root directory; @value{xref-absolute-names}. (Note
+@command{tar} from the root directory; @value{xref-absolute-names}. (Note
also that @file{collection.tar}, the original archive file, has itself
-been archived. @code{tar} will accept any file as a file to be
+been archived. @command{tar} will accept any file as a file to be
archived, regardless of its content. When @file{music.tar} is
extracted, the archive file @file{collection.tar} will be re-written
into the file system).
-If you give @code{tar} a command such as
+If you give @command{tar} a command such as
@example
$ @kbd{tar --create --file=foo.tar .}
@end example
@noindent
-@code{tar} will report @samp{tar: ./foo.tar is the archive; not dumped}.
-This happens because @code{tar} creates the archive @file{foo.tar} in
+@command{tar} will report @samp{tar: ./foo.tar is the archive; not dumped}.
+This happens because @command{tar} creates the archive @file{foo.tar} in
the current directory before putting any files into it. Then, when
-@code{tar} attempts to add all the files in the directory @file{.} to
+@command{tar} attempts to add all the files in the directory @file{.} to
the archive, it notices that the file @file{./foo.tar} is the same as the
archive @file{foo.tar}, and skips it. (It makes no sense to put an archive
-into itself.) GNU @code{tar} will continue in this case, and create the
+into itself.) @sc{gnu} @command{tar} will continue in this case, and create the
archive normally, except for the exclusion of that one file.
-(@emph{Please note:} Other versions of @code{tar} are not so clever;
+(@emph{Please note:} Other versions of @command{tar} are not so clever;
they will enter an infinite loop when this happens, so you should not
-depend on this behavior unless you are certain you are running GNU
-@code{tar}.) @FIXME{bob doesn't like this sentence, since he does it
+depend on this behavior unless you are certain you are running @sc{gnu}
+@command{tar}.) @FIXME{bob doesn't like this sentence, since he does it
all the time, and we've been doing it in the editing passes for this
manual: In general, make sure that the archive is not inside a
directory being dumped.}
-@node list, extract, create, Tutorial
+@node list
@section How to List Archives
Frequently, you will find yourself wanting to determine exactly what a
@end example
@noindent
-The output of @code{tar} would then be:
+The output of @command{tar} would then be:
@example
blues
to specify the name of the archive.
If you use the @value{op-verbose} option with @samp{--list}, then
-@code{tar} will print out a listing reminiscent of @w{@samp{ls -l}},
+@command{tar} will print out a listing reminiscent of @w{@samp{ls -l}},
showing owner, file size, and so forth.
If you had used @value{op-verbose} mode, the example above would look
@cindex File name arguments, using @code{--list} with
@cindex @code{--list} with file name arguments
You can specify one or more individual member names as arguments when
-using @samp{list}. In this case, @code{tar} will only list the
+using @samp{list}. In this case, @command{tar} will only list the
names of members you identify. For example, @w{@kbd{tar --list
--file=afiles.tar apple}} would only print @file{apple}.
@FIXME{we hope the relevant aspects of this will change:}Because
-@code{tar} preserves paths, file names must be specified as they appear
+@command{tar} preserves paths, file names must be specified as they appear
in the archive (ie., relative to the directory from which the archive
was created). Therefore, it is essential when specifying member names
-to @code{tar} that you give the exact member names. For example,
+to @command{tar} that you give the exact member names. For example,
@w{@kbd{tar --list --file=bfiles birds}} would produce an error message
something like @samp{tar: birds: Not found in archive}, because there is
no member named @file{birds}, only one named @file{./birds}. While the
@file{collection.tar}. If you are not sure of the exact file name, try
listing all the files in the archive and searching for the one you
expect to find; remember that if you use @samp{--list} with no file
-names as arguments, @code{tar} will print the names of all the members
+names as arguments, @command{tar} will print the names of all the members
stored in the specified archive.
@menu
* list dir::
@end menu
-@node list dir, , list, list
+@node list dir
@unnumberedsubsec Listing the Contents of a Stored Directory
@UNREVISED
$ @kbd{tar --list --verbose --file=music.tar practice}
@end example
-@code{tar} responds:
+@command{tar} responds:
@example
drwxrwxrwx myself user 0 1990-05-31 21:49 practice/
-rw-rw-rw- myself user 10240 1990-05-31 21:49 practice/collection.tar
@end example
-When you use a directory name as a file name argument, @code{tar} acts on
+When you use a directory name as a file name argument, @command{tar} acts on
all the files (including sub-directories) in that directory.
-@node extract, going further, list, Tutorial
+@node extract
@section How to Extract Members from an Archive
@UNREVISED
@cindex Extraction
* failing commands::
@end menu
-@node extracting archives, extracting files, extract, extract
+@node extracting archives
@subsection Extracting an Entire Archive
To extract an entire archive, specify the archive file name only, with
-rw-rw-rw- me user 20 1996-09-23 16:44 folk
@end example
-@node extracting files, extract dir, extracting archives, extract
+@node extracting files
@subsection Extracting Specific Files
To extract specific archive members, give their exact member names as
you may have made before deleting the file from the file system,
however, will @emph{not} have been made to the archive member.) The
archive file, @samp{collection.tar}, is the same as it was before you
-extracted @samp{blues}. You can confirm this by running @code{tar} with
+extracted @samp{blues}. You can confirm this by running @command{tar} with
@value{op-list}.
@FIXME{we hope this will change:}Remember that as with other operations,
If you give the @value{op-verbose} option, then @value{op-extract} will
print the names of the archive members as it extracts them.
-@node extract dir, failing commands, extracting files, extract
+@node extract dir
@subsection Extracting Files that are Directories
Extracting directories which are members of an archive is similar to
However, if a file was stored with a directory name as part of its file
name, and that directory does not exist under the working directory when
-the file is extracted, @code{tar} will create the directory.
+the file is extracted, @command{tar} will create the directory.
We can demonstrate how to use @samp{--extract} to extract a directory
file with an example. Change to the @file{practice} directory if you
@FIXME{IMPORTANT! show the final structure, here. figure out what it
will be.}
-@node failing commands, , extract dir, extract
+@node failing commands
@subsection Commands That Will Fail
Here are some sample commands you might try which will not work, and why
@FIXME{more examples, here? hag thinks it's a good idea.}
-@node going further, , extract, Tutorial
+@node going further
@section Going Further Ahead in this Manual
@FIXME{need to write up a node here about the things that are going to
be in the rest of the manual.}
-@node tar invocation, operations, Tutorial, Top
-@chapter Invoking GNU @code{tar}
+@node tar invocation
+@chapter Invoking @sc{gnu} @command{tar}
@UNREVISED
-This chapter is about how one invokes the GNU @code{tar} command, from
+This chapter is about how one invokes the @sc{gnu} @command{tar} command, from
the command synopsis (@pxref{Synopsis}). There are numerous options,
and many styles for writing them. One mandatory option specifies
-the operation @code{tar} should perform (@pxref{Operation Summary}),
+the operation @command{tar} should perform (@pxref{Operation Summary}),
other options are meant to detail how this operation should be performed
(@pxref{Option Summary}). Non-option arguments are not always interpreted
the same way, depending on what the operation is.
writing them (@pxref{Styles}). On the other hand, operations and options
are fully described elsewhere, in other chapters. Here, you will find
only synthetic descriptions for operations and options, together with
-pointers to other parts of the @code{tar} manual.
+pointers to other parts of the @command{tar} manual.
Some options are so special they are fully described right in this
chapter. They have the effect of inhibiting the normal operation of
-@code{tar} or else, they globally alter the amount of feedback the user
+@command{tar} or else, they globally alter the amount of feedback the user
receives about what is going on. These are the @value{op-help} and
@value{op-version} (@pxref{help}), @value{op-verbose} (@pxref{verbose})
and @value{op-interactive} options (@pxref{interactive}).
* interactive::
@end menu
-@node Synopsis, using tar options, tar invocation, tar invocation
-@section General Synopsis of @code{tar}
+@node Synopsis
+@section General Synopsis of @command{tar}
-The GNU @code{tar} program is invoked as either one of:
+The @sc{gnu} @command{tar} program is invoked as either one of:
@example
@kbd{tar @var{option}@dots{} [@var{name}]@dots{}}
The second form is for when old options are being used.
-You can use @code{tar} to store files in an archive, to extract them from
+You can use @command{tar} to store files in an archive, to extract them from
an archive, and to do other types of archive manipulation. The primary
-argument to @code{tar}, which is called the @dfn{operation}, specifies
-which action to take. The other arguments to @code{tar} are either
-@dfn{options}, which change the way @code{tar} performs an operation,
+argument to @command{tar}, which is called the @dfn{operation}, specifies
+which action to take. The other arguments to @command{tar} are either
+@dfn{options}, which change the way @command{tar} performs an operation,
or file names or archive members, which specify the files or members
-@code{tar} is to act on.
+@command{tar} is to act on.
You can actually type in arguments in any order, even if in this manual
the options always precede the other arguments, to make examples easier
to understand. Further, the option stating the main operation mode
-(the @code{tar} main command) is usually given first.
+(the @command{tar} main command) is usually given first.
Each @var{name} in the synopsis above is interpreted as an archive member
name when the main command is one of @value{op-compare}, @value{op-delete},
and @value{op-create}, these @var{name} arguments specify the names
of either files or directory hierarchies to place in the archive.
These files or hierarchies should already exist in the file system,
-prior to the execution of the @code{tar} command.
+prior to the execution of the @command{tar} command.
-@code{tar} interprets relative file names as being relative to the
-working directory. @code{tar} will make all file names relative
+@command{tar} interprets relative file names as being relative to the
+working directory. @command{tar} will make all file names relative
(by removing leading slashes when archiving or restoring files),
unless you specify otherwise (using the @value{op-absolute-names}
option). @value{xref-absolute-names}, for more information about
@value{op-absolute-names}.
If you give the name of a directory as either a file name or a member
-name, then @code{tar} acts recursively on all the files and directories
+name, then @command{tar} acts recursively on all the files and directories
beneath that directory. For example, the name @file{/} identifies all
-the files in the filesystem to @code{tar}.
+the files in the filesystem to @command{tar}.
The distinction between file names and archive member names is especially
important when shell globbing is used, and sometimes a source of confusion
for newcomers. @xref{Wildcards}, for more information about globbing.
The problem is that shells may only glob using existing files in the
-file system. Only @code{tar} itself may glob on archive members, so when
-needed, you must ensure that wildcard characters reach @code{tar} without
+file system. Only @command{tar} itself may glob on archive members, so when
+needed, you must ensure that wildcard characters reach @command{tar} without
being interpreted by the shell first. Using a backslash before @samp{*}
or @samp{?}, or putting the whole argument between quotes, is usually
sufficient for this.
If you don't use any file name arguments, @value{op-append},
@value{op-delete} and @value{op-concatenate} will do nothing, while
-@value{op-create} will usually yield a diagnostic and inhibit @code{tar}
-execution. The other operations of @code{tar} (@value{op-list},
+@value{op-create} will usually yield a diagnostic and inhibit @command{tar}
+execution. The other operations of @command{tar} (@value{op-list},
@value{op-extract}, @value{op-compare}, and @value{op-update}) will act
on the entire contents of the archive.
@cindex exit status
@cindex return status
-Besides successful exits, GNU @code{tar} may fail for many reasons.
-Some reasons correspond to bad usage, that is, when the @code{tar}
+Besides successful exits, @sc{gnu} @command{tar} may fail for many reasons.
+Some reasons correspond to bad usage, that is, when the @command{tar}
command is improperly written.
Errors may be encountered later, while encountering an error
processing the archive or the files. Some errors are recoverable,
-in which case the failure is delayed until @code{tar} has completed
+in which case the failure is delayed until @command{tar} has completed
all its work. Some errors are such that it would not meaningful,
-or at least risky, to continue processing: @code{tar} then aborts
+or at least risky, to continue processing: @command{tar} then aborts
processing immediately. All abnormal exits, whether immediate or
delayed, should always be clearly diagnosed on @code{stderr}, after
a line stating the nature of the error.
-GNU @code{tar} returns only a few exit statuses. I'm really
+@sc{gnu} @command{tar} returns only a few exit statuses. I'm really
aiming simplicity in that area, for now. If you are not using the
@value{op-compare} option, zero means that everything went well, besides
maybe innocuous warnings. Nonzero means that something went wrong.
Right now, as of today, ``nonzero'' is almost always 2, except for
remote operations, where it may be 128.
-@node using tar options, Styles, Synopsis, tar invocation
-@section Using @code{tar} Options
+@node using tar options
+@section Using @command{tar} Options
-GNU @code{tar} has a total of eight operating modes which allow you to
+@sc{gnu} @command{tar} has a total of eight operating modes which allow you to
perform a variety of tasks. You are required to choose one operating
-mode each time you employ the @code{tar} program by specifying one, and
-only one operation as an argument to the @code{tar} command (two lists
+mode each time you employ the @command{tar} program by specifying one, and
+only one operation as an argument to the @command{tar} command (two lists
of four operations each may be found at @ref{frequent operations} and
@ref{Operations}). Depending on circumstances, you may also wish to
customize how the chosen operating mode behaves. For example, you may
you wish to archive may require you to do something special in order to
make the archive look right.
-You can customize and control @code{tar}'s performance by running
-@code{tar} with one or more options (such as @value{op-verbose}, which
+You can customize and control @command{tar}'s performance by running
+@command{tar} with one or more options (such as @value{op-verbose}, which
we used in the tutorial). As we said in the tutorial, @dfn{options} are
-arguments to @code{tar} which are (as their name suggests) optional.
+arguments to @command{tar} which are (as their name suggests) optional.
Depending on the operating mode, you may specify one or more options.
Different options will have different effects, but in general they all
change details of the operation, such as archive format, archive name,
others infrequently, or not at all. (A full list of options is
available in @pxref{All Options}.)
-Note that @code{tar} options are case sensitive. For example, the
+Note that @command{tar} options are case sensitive. For example, the
options @samp{-T} and @samp{-t} are different; the first requires an
argument for stating the name of a file providing a list of @var{name}s,
while the second does not require an argument and is another way to
write @value{op-list}.
In addition to the eight operations, there are many options to
-@code{tar}, and three different styles for writing both: long (mnemonic)
+@command{tar}, and three different styles for writing both: long (mnemonic)
form, short form, and old style. These styles are discussed below.
Both the options and the operations can be written in any of these three
styles.
for this chapter; probably do that after stuff from chap. 4 is
incorporated.}
-@node Styles, All Options, using tar options, tar invocation
+@node Styles
@section The Three Option Styles
There are three styles for writing operations and options to the command
-line invoking @code{tar}. The different styles were developed at
-different times during the history of @code{tar}. These styles will be
+line invoking @command{tar}. The different styles were developed at
+different times during the history of @command{tar}. These styles will be
presented below, from the most recent to the oldest.
Some options must take an argument. (For example, @value{op-file} takes
the name of an archive file as an argument. If you do not supply an
-archive file name, @code{tar} will use a default, but this can be
+archive file name, @command{tar} will use a default, but this can be
confusing; thus, we recommend that you always supply a specific archive
file name.) Where you @emph{place} the arguments generally depends on
which style of options you choose. We will detail specific information
* Mixing:: Mixing Option Styles
@end menu
-@node Mnemonic Options, Short Options, Styles, Styles
+@node Mnemonic Options
@subsection Mnemonic Option Style
@FIXME{have to decide whether or ot to replace other occurrences of
@samp{--cre} can be used in place of @samp{--create} because there is no
other mnemonic option which begins with @samp{cre}. (One way to find
this out is by trying it and seeing what happens; if a particular
-abbreviation could represent more than one option, @code{tar} will tell
+abbreviation could represent more than one option, @command{tar} will tell
you that that abbreviation is ambiguous and you'll know that that
abbreviation won't work. You may also choose to run @samp{tar --help}
-to see a list of options. Be aware that if you run @code{tar} with a
+to see a list of options. Be aware that if you run @command{tar} with a
unique abbreviation for the long name of an option you didn't want to
-use, you are stuck; @code{tar} will perform the command as ordered.)
+use, you are stuck; @command{tar} will perform the command as ordered.)
Mnemonic options are meant to be obvious and easy to remember, and their
meanings are generally easier to discern than those of their
@noindent
gives a fairly good set of hints about what the command does, even
-for those not fully acquainted with @code{tar}.
+for those not fully acquainted with @command{tar}.
Mnemonic options which require arguments take those arguments
immediately following the option name; they are introduced by an equal
sign. For example, the @samp{--file} option (which tells the name
-of the @code{tar} archive) is given a file such as @file{archive.tar}
+of the @command{tar} archive) is given a file such as @file{archive.tar}
as argument by using the notation @samp{--file=archive.tar} for the
mnemonic option.
-@node Short Options, Old Options, Mnemonic Options, Styles
+@node Short Options
@subsection Short Option Style
Most options also have a short option name. Short options start with
Short options' letters may be clumped together, but you are not
required to do this (as compared to old options; see below). When short
options are clumped as a set, use one (single) dash for them all, e.g.@:
-@w{@samp{@code{tar} -cvf}}. Only the last option in such a set is allowed
+@w{@samp{@command{tar} -cvf}}. Only the last option in such a set is allowed
to have an argument@footnote{Clustering many options, the last of which
has an argument, is a rather opaque way to write options. Some wonder if
-GNU @code{getopt} should not even be made helpful enough for considering
+@sc{gnu} @code{getopt} should not even be made helpful enough for considering
such usages as invalid.}.
When the options are separated, the argument for each option which requires
that belong to them. If you do not move the arguments properly, you may
end up overwriting files.
-@node Old Options, Mixing, Short Options, Styles
+@node Old Options
@subsection Old Option Style
@UNREVISED
with a dash, you are announcing the short option style instead of the
old option style; short options are decoded differently.}. This set
of letters must be the first to appear on the command line, after the
-@code{tar} program name and some white space; old options cannot appear
+@command{tar} program name and some white space; old options cannot appear
anywhere else. The letter of an old option is exactly the same letter as
the corresponding short option. For example, the old option @samp{t} is
the same as the short option @samp{-t}, and consequently, the same as the
If you want to reorder the letters in the old option argument, be
sure to reorder any corresponding argument appropriately.
-This old way of writing @code{tar} options can surprise even experienced
+This old way of writing @command{tar} options can surprise even experienced
users. For example, the two commands:
@example
second example, however, uses @file{z} as the value for option
@samp{f}---probably not what was intended.
-Old options are kept for compatibility with old versions of @code{tar}.
+Old options are kept for compatibility with old versions of @command{tar}.
This second example could be corrected in many ways, among which the
following are equivalent:
@FIXME{still could explain this better; it's redundant:}
@cindex option syntax, traditional
-As far as we know, all @code{tar} programs, GNU and non-GNU, support
-old options. GNU @code{tar} supports them not only for historical
+As far as we know, all @command{tar} programs, @sc{gnu} and non-@sc{gnu}, support
+old options. @sc{gnu} @command{tar} supports them not only for historical
reasons, but also because many people are used to them. For
-compatibility with Unix @code{tar}, the first argument is always
+compatibility with Unix @command{tar}, the first argument is always
treated as containing command and option letters even if it doesn't
start with @samp{-}. Thus, @samp{tar c} is equivalent to @w{@samp{tar
-c}:} both of them specify the @value{op-create} command to create an
archive.
-@node Mixing, , Old Options, Styles
+@node Mixing
@subsection Mixing Option Styles
-All three styles may be intermixed in a single @code{tar} command, so
-long as the rules for each style are fully respected@footnote{Before GNU
-@code{tar} version 1.11.6, a bug prevented intermixing old style options
+All three styles may be intermixed in a single @command{tar} command, so
+long as the rules for each style are fully respected@footnote{Before @sc{gnu}
+@command{tar} version 1.11.6, a bug prevented intermixing old style options
with mnemonic options in some cases.}. Old style options and either of the
-modern styles of options may be mixed within a single @code{tar} command.
+modern styles of options may be mixed within a single @command{tar} command.
However, old style options must be introduced as the first arguments only,
following the rule for old options (old options must appear directly
-after the @code{tar} command and some white space). Modern options may
+after the @command{tar} command and some white space). Modern options may
be given only after all arguments to the old options have been collected.
If this rule is not respected, a modern option might be falsely interpreted
as the value of the argument to one of the old style options.
These last examples mean something completely different from what the
user intended (judging based on the example in the previous set which
uses long options, whose intent is therefore very clear). The first
-four specify that the @code{tar} archive would be a file named
+four specify that the @command{tar} archive would be a file named
@samp{-c}, @samp{c}, @samp{carchive.tar} or @samp{archive.tarc},
respectively. The first two examples also specify a single non-option,
@var{name} argument having the value @samp{archive.tar}. The last
@samp{h}, or @samp{i}), with no argument value. @FIXME{not sure i liked
the first sentence of this paragraph..}
-@node All Options, help, Styles, tar invocation
-@section All @code{tar} Options
+@node All Options
+@section All @command{tar} Options
The coming manual sections contain an alphabetical listing of all
-@code{tar} operations and options, with brief descriptions and cross
+@command{tar} operations and options, with brief descriptions and cross
references to more in-depth explanations in the body of the manual.
They also contain an alphabetically arranged table of the short option
forms with their corresponding long option. You can use this table as
-a reference for deciphering @code{tar} commands in scripts.
+a reference for deciphering @command{tar} commands in scripts.
@menu
* Operation Summary::
* Short Option Summary::
@end menu
-@node Operation Summary, Option Summary, All Options, All Options
+@node Operation Summary
@subsection Operations
@table @kbd
@item --concatenate
@itemx -A
-Appends other @code{tar} archives to the end of the archive.
+Appends other @command{tar} archives to the end of the archive.
@xref{concatenate}.
@item --create
@itemx -c
-Creates a new @code{tar} archive. @xref{create}.
+Creates a new @command{tar} archive. @xref{create}.
@item --delete
@end table
-@node Option Summary, Short Option Summary, Operation Summary, All Options
-@subsection @code{tar} Options
+@node Option Summary
+@subsection @command{tar} Options
@table @kbd
@item --absolute-names
@itemx -P
-Normally when creating an archive, @code{tar} strips an initial @samp{/} from
+Normally when creating an archive, @command{tar} strips an initial @samp{/} from
member names. This option disables that behavior. @FIXME-xref{}
@item --after-date
@item --atime-preserve
-Tells @code{tar} to preserve the access time field in a file's inode when
+Tells @command{tar} to preserve the access time field in a file's inode when
dumping it. @FIXME-xref{}
@item --backup=@var{backup-type}
-Rather than deleting files from the file system, @code{tar} will back them up
+Rather than deleting files from the file system, @command{tar} will back them up
using simple or numbered backups, depending upon @var{backup-type}.
@FIXME-xref{}
@item --block-number
@itemx -R
-With this option present, @code{tar} prints error messages for read errors
+With this option present, @command{tar} prints error messages for read errors
with the block number in the archive file. @FIXME-xref{}
@item --blocking-factor=@var{blocking}
@itemx -b @var{blocking}
-Sets the blocking factor @code{tar} uses to @var{blocking} x 512 bytes per
+Sets the blocking factor @command{tar} uses to @var{blocking} x 512 bytes per
record. @FIXME-xref{}
@item --bzip2
@itemx -I
-This option tells @code{tar} to read or write archives through @code{bzip2}.
+This option tells @command{tar} to read or write archives through @code{bzip2}.
@FIXME-xref{}
@item --checkpoint
-This option directs @code{tar} to print periodic checkpoint messages as it
+This option directs @command{tar} to print periodic checkpoint messages as it
reads through the archive. Its intended for when you want a visual
-indication that @code{tar} is still running, but don't want to see
+indication that @command{tar} is still running, but don't want to see
@samp{--verbose} output. @FIXME-xref{}
@item --compress
@itemx --uncompress
@itemx -Z
-@code{tar} will use the @code{compress} program when reading or writing the
+@command{tar} will use the @command{compress} program when reading or writing the
archive. This allows you to directly act on archives while saving
space. @FIXME-xref{}
@item --dereference
@itemx -h
-When creating a @code{tar} archive, @code{tar} will archive the file that a symbolic
+When creating a @command{tar} archive, @command{tar} will archive the file that a symbolic
link points to, rather than archiving the symlink. @FIXME-xref{}
@item --directory=@var{dir}
@itemx -C @var{dir}
-When this option is specified, @code{tar} will change its current directory
+When this option is specified, @command{tar} will change its current directory
to @var{dir} before performing any operations. When this option is used
during archive creation, it is order sensitive. @FIXME-xref{}
@item --exclude=@var{pattern}
-When performing operations, @code{tar} will skip files that match
+When performing operations, @command{tar} will skip files that match
@var{pattern}. @FIXME-xref{}
@item --exclude-from=@var{file}
@itemx -X @var{file}
-Similar to @samp{--exclude}, except @code{tar} will use the list of patterns
+Similar to @samp{--exclude}, except @command{tar} will use the list of patterns
in the file @var{file}. @FIXME-xref{}
@item --file=@var{archive}
@itemx -f @var{archive}
-@code{tar} will use the file @var{archive} as the @code{tar} archive it
-performs operations on, rather than @code{tar}'s compilation dependent
+@command{tar} will use the file @var{archive} as the @command{tar} archive it
+performs operations on, rather than @command{tar}'s compilation dependent
default. @FIXME-xref{}
@item --files-from=@var{file}
@itemx -T @var{file}
-@code{tar} will use the contents of @var{file} as a list of archive members
+@command{tar} will use the contents of @var{file} as a list of archive members
or files to operate on, in addition to those specified on the
command-line. @FIXME-xref{}
@item --force-local
-Forces @code{tar} to interpret the filename given to @samp{--file} as a local
+Forces @command{tar} to interpret the filename given to @samp{--file} as a local
file, even if it looks like a remote tape drive name. @FIXME-xref{}
@item --group=@var{group}
-Files added to the @code{tar} archive will have a group id of @var{group},
+Files added to the @command{tar} archive will have a group id of @var{group},
rather than the group from the source file. @var{group} is first decoded
as a group symbolic name, but if this interpretation fails, it has to be
a decimal numeric group ID. @FIXME-xref{}
@itemx --ungzip
@itemx -z
-This option tells @code{tar} to read or write archives through @code{gzip},
-allowing @code{tar} to directly operate on several kinds of compressed
+This option tells @command{tar} to read or write archives through @command{gzip},
+allowing @command{tar} to directly operate on several kinds of compressed
archives transparently. @FIXME-xref{}
@item --help
-@code{tar} will print out a short message summarizing the operations and
-options to @code{tar} and exit. @FIXME-xref{}
+@command{tar} will print out a short message summarizing the operations and
+options to @command{tar} and exit. @FIXME-xref{}
@item --ignore-failed-read
-Instructs @code{tar} to exit successfully if it encounters an
-unreadable file. @xref{Reading}.
-
-@item --ignore-umask
-@FIXME{does this exist?}
-
-(See @samp{--preserve-permissions}; @pxref{Writing}.)
+Do not exit unsuccessfully merely because an unreadable file was encountered.
+@xref{Reading}.
@item --ignore-zeros
@itemx -i
-With this option, @code{tar} will ignore zeroed blocks in the archive, which
+With this option, @command{tar} will ignore zeroed blocks in the archive, which
normally signals EOF. @xref{Reading}.
@item --incremental
@itemx -G
-Used to inform @code{tar} that it is working with an old GNU-format
+Used to inform @command{tar} that it is working with an old @sc{gnu}-format
incremental backup archive. It is intended primarily for backwards
compatibility only. @FIXME-xref{}
@itemx --new-volume-script=@var{script-file}
@itemx -F @var{script-file}
-When @code{tar} is performing multi-tape backups, @var{script-file} is run
+When @command{tar} is performing multi-tape backups, @var{script-file} is run
at the end of each tape. @FIXME-xref{}
@item --interactive
@itemx --confirmation
@itemx -w
-Specifies that @code{tar} should ask the user for confirmation before
+Specifies that @command{tar} should ask the user for confirmation before
performing potentially destructive options, such as overwriting files.
@FIXME-xref{}
@item --keep-old-files
@itemx -k
-When extracting files from an archive, @code{tar} will not overwrite existing
+When extracting files from an archive, @command{tar} will not overwrite existing
files if this option is present. @xref{Writing}.
@item --label=@var{name}
@itemx -V @var{name}
-When creating an archive, instructs @code{tar} to write @var{name} as a name
-record in the archive. When extracting or listing archives, @code{tar} will
+When creating an archive, instructs @command{tar} to write @var{name} as a name
+record in the archive. When extracting or listing archives, @command{tar} will
only operate on archives that have a label matching the pattern
specified in @var{name}. @FIXME-xref{}
@itemx -g @var{snapshot-file}
During a @samp{--create} operation, specifies that the archive that
-@code{tar} creates is a new GNU-format incremental backup, using
+@command{tar} creates is a new @sc{gnu}-format incremental backup, using
@var{snapshot-file} to determine which files to backup.
-With other operations, informs @code{tar} that the archive is in incremental
+With other operations, informs @command{tar} that the archive is in incremental
format. @FIXME-xref{}
@item --mode=@var{permissions}
-When adding files to an archive, @code{tar} will use @var{permissions}
+When adding files to an archive, @command{tar} will use @var{permissions}
for the archive members, rather than the permissions from the files.
-The program @code{chmod} and this @code{tar} option share the same syntax
+The program @command{chmod} and this @command{tar} option share the same syntax
for what @var{permissions} might be. @xref{File permissions, Permissions,
-File permissions, fileutils, GNU file utilities}. This reference also
+File permissions, fileutils, @sc{gnu} file utilities}. This reference also
has useful information for those not being overly familiar with the Unix
permission system.
@item --multi-volume
@itemx -M
-Informs @code{tar} that it should create or otherwise operate on a
-multi-volume @code{tar} archive. @FIXME-xref{}
+Informs @command{tar} that it should create or otherwise operate on a
+multi-volume @command{tar} archive. @FIXME-xref{}
@item --new-volume-script
@itemx --after-date=@var{date}
@itemx -N
-When creating an archive, @code{tar} will only add files that have changed
+When creating an archive, @command{tar} will only add files that have changed
since @var{date}. @FIXME-xref{}
@item --newer-mtime
-In conjunction with @samp{--newer}, @code{tar} will only add files whose
+In conjunction with @samp{--newer}, @command{tar} will only add files whose
contents have changed (as opposed to just @samp{--newer}, which will
also back up files for which any status information has changed).
@item --no-recursion
-With this option, @code{tar} will not recurse into directories unless a
-directory is explicitly named as an argument to @code{tar}. @FIXME-xref{}
+With this option, @command{tar} will not recurse into directories unless a
+directory is explicitly named as an argument to @command{tar}. @FIXME-xref{}
@item --no-same-owner
When extracting an archive, do not attempt to preserve the owner
-specified in the @code{tar} archive. This the default behavior
+specified in the @command{tar} archive. This the default behavior
for ordinary users; this option has an effect only for the superuser.
@item --no-same-permissions
@item --null
-When @code{tar} is using the @samp{--files-from} option, this option
-instructs @code{tar} to expect filenames terminated with @kbd{NUL}, so
-@code{tar} can correctly work with file names that contain newlines.
+When @command{tar} is using the @samp{--files-from} option, this option
+instructs @command{tar} to expect filenames terminated with @kbd{NUL}, so
+@command{tar} can correctly work with file names that contain newlines.
@FIXME-xref{}
@item --numeric-owner
-This option will notify @code{tar} that it should use numeric user and group
-IDs when creating a @code{tar} file, rather than names. @FIXME-xref{}
+This option will notify @command{tar} that it should use numeric user and group
+IDs when creating a @command{tar} file, rather than names. @FIXME-xref{}
@item --old-archive
@item --one-file-system
@itemx -l
-Used when creating an archive. Prevents @code{tar} from recursing into
+Used when creating an archive. Prevents @command{tar} from recursing into
directories that are on different file systems from the current
directory. @FIXME-xref{}
@item --owner=@var{user}
-Specifies that @code{tar} should use @var{user} as the owner of members
+Specifies that @command{tar} should use @var{user} as the owner of members
when creating archives, instead of the user associated with the source
file. @var{user} is first decoded as a user symbolic name, but if
this interpretation fails, it has to be a decimal numeric user ID.
their distributions for the owner of files, because the @code{root} user is
anonymous anyway, so that might as well be the owner of anonymous archives.
+This option does not affect extraction from archives.
+
@item --portability
@itemx --old-archive
@itemx -o
-Tells @code{tar} to create an archive that is compatible with Unix V7
-@code{tar}. @FIXME-xref{}
+Tells @command{tar} to create an archive that is compatible with Unix V7
+@command{tar}. @FIXME-xref{}
@item --posix
-Instructs @code{tar} to create a POSIX compliant @code{tar} archive. @FIXME-xref{}
+Instructs @command{tar} to create a @sc{posix} compliant @command{tar} archive. @FIXME-xref{}
@item --preserve
@itemx --same-permissions
@itemx -p
-When @code{tar} is extracting an archive, it normally subtracts the users'
+When @command{tar} is extracting an archive, it normally subtracts the users'
umask from the permissions specified in the archive and uses that
number as the permissions to create the destination file. Specifying
-this option instructs @code{tar} that it should use the permissions directly
+this option instructs @command{tar} that it should use the permissions directly
from the archive. @xref{Writing}.
@item --read-full-records
@itemx -B
-Specifies that @code{tar} should reblock its input, for reading from pipes on
+Specifies that @command{tar} should reblock its input, for reading from pipes on
systems with buggy implementations. @xref{Reading}.
@item --record-size=@var{size}
-Instructs @code{tar} to use @var{size} bytes per record when accessing the
+Instructs @command{tar} to use @var{size} bytes per record when accessing the
archive. @FIXME-xref{}
@item --recursive-unlink
@item --remove-files
-Directs @code{tar} to remove the source file from the file system after
+Directs @command{tar} to remove the source file from the file system after
appending it to an archive. @FIXME-xref{}
@item --rsh-command=@var{cmd}
-Notifies @code{tar} that is should use @var{cmd} to communicate with remote
+Notifies @command{tar} that is should use @var{cmd} to communicate with remote
devices. @FIXME-xref{}
@item --same-order
@itemx --preserve-order
@itemx -s
-This option is an optimization for @code{tar} when running on machines with
-small amounts of memory. It informs @code{tar} that the list of file
+This option is an optimization for @command{tar} when running on machines with
+small amounts of memory. It informs @command{tar} that the list of file
arguments has already been sorted to match the order of files in the
archive. @xref{Reading}.
@item --same-owner
-When extracting an archive, @code{tar} will attempt to preserve the owner
-specified in the @code{tar} archive with this option present.
+When extracting an archive, @command{tar} will attempt to preserve the owner
+specified in the @command{tar} archive with this option present.
This is the default behavior for the superuser; this option has an
effect only for ordinary users. @FIXME-xref{}
@item --show-omitted-dirs
-Instructs @code{tar} to mention directories its skipping over when operating
-on a @code{tar} archive. @FIXME-xref{}
+Instructs @command{tar} to mention directories its skipping over when operating
+on a @command{tar} archive. @FIXME-xref{}
@item --sparse
@itemx -S
-Invokes a GNU extension when adding files to an archive that handles
+Invokes a @sc{gnu} extension when adding files to an archive that handles
sparse files efficiently. @FIXME-xref{}
@item --starting-file=@var{name}
@itemx -K @var{name}
-This option affects extraction only; @code{tar} will skip extracting
+This option affects extraction only; @command{tar} will skip extracting
files in the archive until it finds one that matches @var{name}.
@xref{Scarce}.
@item --suffix=@var{suffix}
-Alters the suffix @code{tar} uses when backing up files from the default
+Alters the suffix @command{tar} uses when backing up files from the default
@samp{~}. @FIXME-xref{}
@item --tape-length=@var{num}
@itemx -L @var{num}
-Specifies the length of tapes that @code{tar} is writing as being
+Specifies the length of tapes that @command{tar} is writing as being
@w{@var{num} x 1024} bytes long. @FIXME-xref{}
@item --to-stdout
@itemx -O
-During extraction, @code{tar} will extract files to stdout rather than to the
+During extraction, @command{tar} will extract files to stdout rather than to the
file system. @xref{Writing}.
@item --totals
@item --unlink-first
@itemx -U
-Directs @code{tar} to remove the corresponding file from the file system
+Directs @command{tar} to remove the corresponding file from the file system
before extracting it from the archive. @xref{Writing}.
@item --use-compress-program=@var{prog}
-Instructs @code{tar} to access the archive through @var{prog}, which is
+Instructs @command{tar} to access the archive through @var{prog}, which is
presumed to be a compression program of some sort. @FIXME-xref{}
@item --verbose
@itemx -v
-Specifies that @code{tar} should be more verbose about the operations its
+Specifies that @command{tar} should be more verbose about the operations its
performing. This option can be specified multiple times for some
operations to increase the amount of information displayed. @FIXME-xref{}
@item --version
-@code{tar} will print an informational message about what version it is and a
+@command{tar} will print an informational message about what version it is and a
copyright message, some credits, and then exit. @FIXME-xref{}
@item --volno-file=@var{file}
-Used in conjunction with @samp{--multi-volume}. @code{tar} will keep track
+Used in conjunction with @samp{--multi-volume}. @command{tar} will keep track
of which volume of a multi-volume archive its working in @var{file}.
@FIXME-xref{}
@end table
-@node Short Option Summary, , Option Summary, All Options
+@node Short Option Summary
@subsection Short Options Cross Reference
Here is an alphabetized list of all of the short option forms, matching
@end table
-@node help, verbose, All Options, tar invocation
-@section GNU @code{tar} documentation
+@node help
+@section @sc{gnu} @command{tar} documentation
-Being careful, the first thing is really checking that you are using GNU
-@code{tar}, indeed. The @value{op-version} option will generate a message
-giving confirmation that you are using GNU @code{tar}, with the precise
-version of GNU @code{tar} you are using. @code{tar} identifies itself
+Being careful, the first thing is really checking that you are using @sc{gnu}
+@command{tar}, indeed. The @value{op-version} option will generate a message
+giving confirmation that you are using @sc{gnu} @command{tar}, with the precise
+version of @sc{gnu} @command{tar} you are using. @command{tar} identifies itself
and prints the version number to the standard output, then immediately
exits successfully, without doing anything else, ignoring all other
options. For example, @w{@samp{tar --version}} might return:
@example
-tar (GNU tar) @value{VERSION}
+tar (@sc{gnu} tar) @value{VERSION}
@end example
@noindent
The first occurrence of @samp{tar} in the result above is the program
-name in the package (for example, @code{rmt} is another program), while
+name in the package (for example, @command{rmt} is another program), while
the second occurrence of @samp{tar} is the name of the package itself,
containing possibly many programs. The package is currently named
@samp{tar}, after the name of the main program it contains@footnote{There
-are plans to merge the @code{cpio} and @code{tar} packages into a single one
+are plans to merge the @command{cpio} and @command{tar} packages into a single one
which would be called @code{paxutils}. So, who knows if, one of this days,
-the @value{op-version} would not yield @w{@samp{tar (GNU paxutils) 3.2}}}.
+the @value{op-version} would not yield @w{@samp{tar (@sc{gnu} paxutils) 3.2}}}.
Another thing you might want to do is checking the spelling or meaning
-of some particular @code{tar} option, without resorting to this manual,
-for once you have carefully read it. GNU @code{tar} has a short help
+of some particular @command{tar} option, without resorting to this manual,
+for once you have carefully read it. @sc{gnu} @command{tar} has a short help
feature, triggerable through the @value{op-help} option. By using this
-option, @code{tar} will print a usage message listing all available
+option, @command{tar} will print a usage message listing all available
options on standard output, then exit successfully, without doing
anything else and ignoring all other options. Even if this is only a
brief summary, it may be several screens long. So, if you are not
@end example
@noindent
-presuming, here, that you like using @code{less} for a pager. Other
-popular pagers are @code{more} and @code{pg}. If you know about some
+presuming, here, that you like using @command{less} for a pager. Other
+popular pagers are @command{more} and @command{pg}. If you know about some
@var{keyword} which interests you and do not want to read all the
@value{op-help} output, another common idiom is doing:
The short help output is quite succinct, and you might have to get back
to the full documentation for precise points. If you are reading this
-paragraph, you already have the @code{tar} manual in some form. This
+paragraph, you already have the @command{tar} manual in some form. This
manual is available in printed form, as a kind of small book. It may
-printed out of the GNU @code{tar} distribution, provided you have @TeX{}
+printed out of the @sc{gnu} @command{tar} distribution, provided you have @TeX{}
already installed somewhere, and a laser printer around. Just configure
the distribution, execute the command @w{@samp{make dvi}}, then print
@file{doc/tar.dvi} the usual way (contact your local guru to know how).
-If GNU @code{tar} has been conveniently installed at your place, this
+If @sc{gnu} @command{tar} has been conveniently installed at your place, this
manual is also available in interactive, hypertextual form as an Info
file. Just call @w{@samp{info tar}} or, if you do not have the
-@code{info} program handy, use the Info reader provided within GNU
+@command{info} program handy, use the Info reader provided within @sc{gnu}
Emacs, calling @samp{tar} from the main Info menu.
-There is currently no @code{man} page for GNU @code{tar}. If you observe
+There is currently no @code{man} page for @sc{gnu} @command{tar}. If you observe
such a @code{man} page on the system you are running, either it does not
-long to GNU @code{tar}, or it has not been produced by GNU. Currently,
-GNU @code{tar} documentation is provided in Texinfo format only, if we
+long to @sc{gnu} @command{tar}, or it has not been produced by @sc{gnu}. Currently,
+@sc{gnu} @command{tar} documentation is provided in Texinfo format only, if we
except, of course, the short result of @kbd{tar --help}.
-@node verbose, interactive, help, tar invocation
-@section Checking @code{tar} progress
+@node verbose
+@section Checking @command{tar} progress
@cindex Progress information
@cindex Status information
@cindex Verbose operation
@cindex Block number where error occurred
@cindex Error message, block number of
-@cindex Version of the @code{tar} program
+@cindex Version of the @command{tar} program
@cindex Getting more information during the operation
@cindex Information during operation
-@cindex Feedback from @code{tar}
+@cindex Feedback from @command{tar}
-Typically, @code{tar} performs most operations without reporting any
-information to the user except error messages. When using @code{tar}
+Typically, @command{tar} performs most operations without reporting any
+information to the user except error messages. When using @command{tar}
with many options, particularly ones with complicated or
difficult-to-predict behavior, it is possible to make serious mistakes.
-@code{tar} provides several options that make observing @code{tar}
-easier. These options cause @code{tar} to print information as it
+@command{tar} provides several options that make observing @command{tar}
+easier. These options cause @command{tar} to print information as it
progresses in its job, and you might want to use them just for being
more careful about what is going on, or merely for entertaining
yourself. If you have encountered a problem when operating on an
Normally, the @value{op-list} command to list an archive prints just
the file names (one per line) and the other commands are silent.
When used with most operations, the @value{op-verbose} option causes
-@code{tar} to print the name of each file or archive member as it
-is processed. This and the other options which make @code{tar} print
-status information can be useful in monitoring @code{tar}.
+@command{tar} to print the name of each file or archive member as it
+is processed. This and the other options which make @command{tar} print
+status information can be useful in monitoring @command{tar}.
With @value{op-create} or @value{op-extract}, @value{op-verbose} used once
just prints the names of the files or members as they are processed.
-Using it twice causes @code{tar} to print a longer listing (reminiscent
+Using it twice causes @command{tar} to print a longer listing (reminiscent
of @samp{ls -l}) for each member. Since @value{op-list} already prints
the names of the members, @value{op-verbose} used once with @value{op-list}
-causes @code{tar} to print an @samp{ls -l} type listing of the files
+causes @command{tar} to print an @samp{ls -l} type listing of the files
in the archive. The following examples both extract members with
long list output:
being written to the standard output, as with @samp{tar --create
--file=- --verbose} (@samp{tar cfv -}, or even @samp{tar cv}---if the
installer let standard output be the default archive). In that case
-@code{tar} writes verbose output to the standard error stream.
+@command{tar} writes verbose output to the standard error stream.
The @value{op-totals} option---which is only meaningful when used with
-@value{op-create}---causes @code{tar} to print the total
+@value{op-create}---causes @command{tar} to print the total
amount written to the archive, after it has been fully created.
The @value{op-checkpoint} option prints an occasional message
-as @code{tar} reads or writes the archive. In fact, it print
+as @command{tar} reads or writes the archive. In fact, it print
directory names while reading the archive. It is designed for
those who don't need the more detailed (and voluminous) output of
-@value{op-block-number}, but do want visual confirmation that @code{tar}
+@value{op-block-number}, but do want visual confirmation that @command{tar}
is actually making forward progress.
@FIXME{There is some confusion here. It seems that -R once wrote a
it might be excluded by the use of the @value{op-exclude} option, or
some other reason.
-If @value{op-block-number} is used, @code{tar} prints, along with every
+If @value{op-block-number} is used, @command{tar} prints, along with every
message it would normally produce, the block number within the archive
where the message was triggered. Also, supplementary messages are
triggered when reading blocks full of NULs, or when hitting end of file on
the archive. As of now, if the archive if properly terminated with a NUL
block, the reading of the file may stop before end of file is met, so the
position of end of file will not usually show when @value{op-block-number}
-is used. Note that GNU @code{tar} drains the archive before exiting when
+is used. Note that @sc{gnu} @command{tar} drains the archive before exiting when
reading the archive from a pipe.
This option is especially useful when reading damaged archives, since
front of the tape). @FIXME-xref{when the node name is set and the
backup section written.}
-@node interactive, , verbose, tar invocation
+@node interactive
@section Asking for Confirmation During Operations
@cindex Interactive operation
-Typically, @code{tar} carries out a command without stopping for
+Typically, @command{tar} carries out a command without stopping for
further instructions. In some situations however, you may want to
exclude some files and archive members from the operation (for instance
if disk or storage space is tight). You can do this by excluding
certain files automatically (@pxref{Choosing}), or by performing
an operation interactively, using the @value{op-interactive} option.
-@code{tar} also accepts @samp{--confirmation} for this option.
+@command{tar} also accepts @samp{--confirmation} for this option.
When the @value{op-interactive} option is specified, before
-reading, writing, or deleting files, @code{tar} first prints a message
+reading, writing, or deleting files, @command{tar} first prints a message
for each such file, telling what operation it intends to take, then asks
for confirmation on the terminal. The actions which require
confirmation include adding a file to the archive, extracting a file
from the archive, deleting a file from the archive, and deleting a file
from disk. To confirm the action, you must type a line of input
beginning with @samp{y}. If your input line begins with anything other
-than @samp{y}, @code{tar} skips that file.
+than @samp{y}, @command{tar} skips that file.
-If @code{tar} is reading the archive from the standard input,
-@code{tar} opens the file @file{/dev/tty} to support the interactive
+If @command{tar} is reading the archive from the standard input,
+@command{tar} opens the file @file{/dev/tty} to support the interactive
communications.
Verbose output is normally sent to standard output, separate from
read from that named pipe. This has the advantage of letting standard
output free to receive verbose output, all separate from errors.
-@node operations, Backups, tar invocation, Top
-@chapter GNU @code{tar} Operations
+@node operations
+@chapter @sc{gnu} @command{tar} Operations
@menu
* Basic tar::
* Advanced tar::
+* create options::
* extract options::
* backup::
* Applications::
* looking ahead::
@end menu
-@node Basic tar, Advanced tar, operations, operations
-@section Basic GNU @code{tar} Operations
+@node Basic tar
+@section Basic @sc{gnu} @command{tar} Operations
-The basic @code{tar} operations, @value{op-create}, @value{op-list} and
+The basic @command{tar} operations, @value{op-create}, @value{op-list} and
@value{op-extract}, are currently presented and described in the tutorial
chapter of this manual. This section provides some complementary notes
for these operations.
initialize an empty archive and later use @value{op-append} for adding
all members. Some applications would not welcome making an exception
in the way of adding the first archive member. On the other hand,
-many people reported that it is dangerously too easy for @code{tar}
+many people reported that it is dangerously too easy for @command{tar}
to destroy a magnetic tape with an empty archive@footnote{This is well
described in @cite{Unix-haters Handbook}, by Simson Garfinkel, Daniel
Weise & Steven Strassmann, IDG Books, ISBN 1-56884-203-1.}. The two most
@end enumerate
So, recognizing the likelihood and the catastrophical nature of these
-errors, GNU @code{tar} now takes some distance from elegance, and
+errors, @sc{gnu} @command{tar} now takes some distance from elegance, and
cowardly refuses to create an archive when @value{op-create} option is
given, there are no arguments besides options, and @value{op-files-from}
-option is @emph{not} used. To get around the cautiousness of GNU
-@code{tar} and nevertheless create an archive with nothing in it,
+option is @emph{not} used. To get around the cautiousness of @sc{gnu}
+@command{tar} and nevertheless create an archive with nothing in it,
one may still use, as the value for the @value{op-files-from} option,
a file with no names in it, as shown in the following commands:
@item @value{op-extract}
-A socket is stored, within a GNU @code{tar} archive, as a pipe.
+A socket is stored, within a @sc{gnu} @command{tar} archive, as a pipe.
@item @value{op-list}
-GNU @code{tar} now shows dates as @samp{1996-11-09}, while it used to
+@sc{gnu} @command{tar} now shows dates as @samp{1996-11-09}, while it used to
show them as @samp{Nov 11 1996}. (One can revert to the old behavior by
defining @code{USE_OLD_CTIME} in @file{src/list.c} before reinstalling.)
But preferably, people should get used to ISO 8601 dates. Local
@end table
-@node Advanced tar, extract options, Basic tar, operations
-@section Advanced GNU @code{tar} Operations
+@node Advanced tar
+@section Advanced @sc{gnu} @command{tar} Operations
-Now that you have learned the basics of using GNU @code{tar}, you may
-want to learn about further ways in which @code{tar} can help you.
+Now that you have learned the basics of using @sc{gnu} @command{tar}, you may
+want to learn about further ways in which @command{tar} can help you.
This chapter presents five, more advanced operations which you probably
won't use on a daily basis, but which serve more specialized functions.
We also explain the different styles of options and why you might want
-to use one or another, or a combination of them in your @code{tar}
+to use one or another, or a combination of them in your @command{tar}
commands. Additionally, this chapter includes options which allow you to
-define the output from @code{tar} more carefully, and provide help and
+define the output from @command{tar} more carefully, and provide help and
error correction in special circumstances.
@FIXME{check this after the chapter is actually revised to make sure
* compare::
@end menu
-@node Operations, current state, Advanced tar, Advanced tar
-@subsection The Five Advanced @code{tar} Operations
+@node Operations
+@subsection The Five Advanced @command{tar} Operations
@UNREVISED
In the last chapter, you learned about the first three operations to
-@code{tar}. This chapter presents the remaining five operations to
-@code{tar}: @samp{--append}, @samp{--update}, @samp{--concatenate},
+@command{tar}. This chapter presents the remaining five operations to
+@command{tar}: @samp{--append}, @samp{--update}, @samp{--concatenate},
@samp{--delete}, and @samp{--compare}.
You are not likely to use these operations as frequently as those
Compare archive members to their counterparts in the file system.
@end table
-@node current state, append, Operations, Advanced tar
-@ifinfo
+@node current state
@subsection The Current State of the Practice Files
-@end ifinfo
-Currently, the listing of the directory using @code{ls} is as follows:
+Currently, the listing of the directory using @command{ls} is as follows:
@example
@FIXME{need to fill in the above!!!}
-@node append, update, current state, Advanced tar
+@node append
@subsection How to Add Files to Existing Archives: @code{--append}
@UNREVISED
If you use @value{op-append} to add a file that has the same name as an
archive member to an archive containing that archive member, then the
old member is not deleted. What does happen, however, is somewhat
-complex. @code{tar} @emph{allows} you to have infinite numbers of files
+complex. @command{tar} @emph{allows} you to have infinite numbers of files
with the same name. Some operations treat these same-named members no
differently than any other set of archive members: for example, if you
view an archive with @value{op-list}, you will see all of those members
@samp{--extract} extracts an archive in the order the members appeared
in the archive; the most recently archived members will be extracted
last. Additionally, an extracted member will @emph{overwrite} a file of
-the same name which existed in the directory already, and @code{tar}
+the same name which existed in the directory already, and @command{tar}
will not prompt you about this. Thus, only the most recently archived
member will end up being extracted, as it will overwrite the one
extracted before it, and so on.
* multiple::
@end menu
-@node appending files, multiple, append, append
+@node appending files
@subsubsection Appending Files to an Archive
@UNREVISED
@cindex Adding files to an Archive
@samp{--append} cannot be performed on some tape drives, unfortunately,
due to deficiencies in the formats those tape drives use. The archive
-must be a valid @code{tar} archive, or else the results of using this
+must be a valid @command{tar} archive, or else the results of using this
operation will be unpredictable. @xref{Media}.
To demonstrate using @samp{--append} to add a file to an archive,
create a file called @file{rock} in the @file{practice} directory.
Make sure you are in the @file{practice} directory. Then, run the
-following @code{tar} command to add @file{rock} to
+following @command{tar} command to add @file{rock} to
@file{collection.tar}:
@example
@FIXME{in theory, dan will (soon) try to turn this node into what it's
title claims it will become...}
-@node multiple, , appending files, append
+@node multiple
@subsubsection Multiple Files with the Same Name
You can use @value{op-append} to add copies of files which have been
updated since the archive was created. (However, we do not recommend
-doing this since there is another @code{tar} option called
+doing this since there is another @command{tar} option called
@samp{--update}; @pxref{update} for more information. We describe this
use of @samp{--append} here for the sake of completeness.) @FIXME{is
this really a good idea, to give this whole description for something
@end example
@noindent
-Because you specified the @samp{--verbose} option, @code{tar} has
+Because you specified the @samp{--verbose} option, @command{tar} has
printed the name of the file being appended as it was acted on. Now
list the contents of the archive:
you employ the @value{op-backup} option. @FIXME-ref{Multiple Members
with the Same Name}.)
-@node update, concatenate, append, Advanced tar
+@node update
@subsection Updating an Archive
@UNREVISED
@cindex Updating an archive
In the previous section, you learned how to use @value{op-append} to add
a file to an existing archive. A related operation is
-@value{op-update}. The @samp{--update} operation updates a @code{tar}
+@value{op-update}. The @samp{--update} operation updates a @command{tar}
archive by comparing the date of the specified archive members against
the date of the file with the same name. If the file has been modified
more recently than the archive member, then the newer version of the
* how to update::
@end menu
-@node how to update, , update, update
+@node how to update
@subsubsection How to Update an Archive Using @code{--update}
You must use file name arguments with the @value{op-update} operation.
-If you don't specify any files, @code{tar} won't act on any files and
+If you don't specify any files, @command{tar} won't act on any files and
won't tell you that it didn't do anything (which may end up confusing
you).
To see the @samp{--update} option at work, create a new file,
@file{classical}, in your practice directory, and some extra text to the
-file @file{blues}, using any text editor. Then invoke @code{tar} with
+file @file{blues}, using any text editor. Then invoke @command{tar} with
the @samp{update} operation and the @value{op-verbose} option specified,
using the names of all the files in the practice directory as file name
arguments:
@end example
@noindent
-Because we have specified verbose mode, @code{tar} prints out the names
+Because we have specified verbose mode, @command{tar} prints out the names
of the files it is working on, which in this case are the names of the
files that needed to be updated. If you run @samp{tar --list} and look
at the archive, you will see @file{blues} and @file{classical} at its
the one at the end will be newer and larger, since you added text before
updating it.
-(The reason @code{tar} does not overwrite the older file when updating
+(The reason @command{tar} does not overwrite the older file when updating
it is because writing to the middle of a section of tape is a difficult
process. Tapes are not designed to go backward. @xref{Media}, for more
information about tapes.
@value{op-update} is not suitable for performing backups for two
reasons: it does not change directory content entries, and it lengthens
-the archive every time it is used. The GNU @code{tar} options intended
+the archive every time it is used. The @sc{gnu} @command{tar} options intended
specifically for backups are more efficient. If you need to run
backups, please consult @ref{Backups}.
-@node concatenate, delete, update, Advanced tar
+@node concatenate
@subsection Combining Archives with @code{--concatenate}
@cindex Adding archives to an archive
-rw-rw-rw- melissa user 65 1997-01-30 14:15 jazz
@end example
-We can concatenate these two archives with @code{tar}:
+We can concatenate these two archives with @command{tar}:
@example
$ @kbd{cd ..}
Like @value{op-append}, this operation cannot be performed on some
tape drives, due to deficiencies in the formats those tape drives use.
-@cindex @code{concatenate} vs @code{cat}
-@cindex @code{cat} vs @code{concatenate}
-It may seem more intuitive to you to want or try to use @code{cat} to
+@cindex @code{concatenate} vs @command{cat}
+@cindex @command{cat} vs @code{concatenate}
+It may seem more intuitive to you to want or try to use @command{cat} to
concatenate two archives instead of using the @samp{--concatenate}
-operation; after all, @code{cat} is the utility for combining files.
+operation; after all, @command{cat} is the utility for combining files.
-However, @code{tar} archives incorporate an end-of-file marker which
+However, @command{tar} archives incorporate an end-of-file marker which
must be removed if the concatenated archives are to be read properly as
one archive. @samp{--concatenate} removes the end-of-archive marker
from the target archive before each new archive is appended. If you use
-@code{cat} to combine the archives, the result will not be a valid
-@code{tar} format archive. If you need to retrieve files from an
-archive that was added to using the @code{cat} utility, use the
+@command{cat} to combine the archives, the result will not be a valid
+@command{tar} format archive. If you need to retrieve files from an
+archive that was added to using the @command{cat} utility, use the
@value{op-ignore-zeros} option. @xref{Ignore Zeros}, for further
information on dealing with archives improperly combined using the
-@code{cat} shell utility.
+@command{cat} shell utility.
@FIXME{this shouldn't go here. where should it go?} You must specify
the source archives using @value{op-file} (@value{pxref-file}). If you
-do not specify the target archive, @code{tar} uses the value of the
-environment variable @code{TAPE}, or, if this has not been set, the
+do not specify the target archive, @command{tar} uses the value of the
+environment variable @env{TAPE}, or, if this has not been set, the
default archive name.
-@node delete, compare, concatenate, Advanced tar
+@node delete
@subsection Removing Archive Members Using @samp{--delete}
@UNREVISED
@cindex Deleting files from an archive
option. Specify the name of the archive with @value{op-file} and then
specify the names of the members to be deleted; if you list no member
names, nothing will be deleted. The @value{op-verbose} option will
-cause @code{tar} to print the names of the members as they are deleted.
+cause @command{tar} to print the names of the members as they are deleted.
As with @value{op-extract}, you must give the exact member names when
using @samp{tar --delete}. @samp{--delete} will remove all versions of
the named file from the archive. The @samp{--delete} operation can run
follow it and see what it actually does!}
The @value{op-delete} option has been reported to work properly when
-@code{tar} acts as a filter from @code{stdin} to @code{stdout}.
+@command{tar} acts as a filter from @code{stdin} to @code{stdout}.
-@node compare, , delete, Advanced tar
+@node compare
@subsection Comparing Archive Members with the File System
@cindex Verifying the currency of an archive
@UNREVISED
specified archive members against files with the same names, and then
reports differences in file size, mode, owner, modification date and
contents. You should @emph{only} specify archive member names, not file
-names. If you do not name any members, then @code{tar} will compare the
+names. If you do not name any members, then @command{tar} will compare the
entire archive. If a file is represented in the archive but does not
-exist in the file system, @code{tar} reports a difference.
+exist in the file system, @command{tar} reports a difference.
You have to specify the record size of the archive when modifying an
archive with a non-default record size.
-@code{tar} ignores files in the file system that do not have
+@command{tar} ignores files in the file system that do not have
corresponding members in the archive.
The following example compares the archive members @file{rock},
@file{blues} and @file{funk} in the archive @file{bluesrock.tar} with
files of the same name in the file system. (Note that there is no file,
-@file{funk}; @code{tar} will report an error message.)
+@file{funk}; @command{tar} will report an error message.)
@example
$ @kbd{tar --compare --file=bluesrock.tar rock blues funk}
@noindent
@FIXME{what does this actually depend on? i'm making a guess,
-here.}Depending on the system where you are running @code{tar} and the
-version you are running, @code{tar} may have a different error message,
+here.}Depending on the system where you are running @command{tar} and the
+version you are running, @command{tar} may have a different error message,
such as:
@example
archive represents the current state of files on disk, more than validating
the integrity of the archive media. For this later goal, @xref{verify}.
-@node extract options, backup, Advanced tar, operations
+@node create options
+@section Options Used by @code{--create}
+
+The previous chapter described the basics of how to use
+@value{op-create} to create an archive from a set of files.
+@xref{create}. This section described advanced options to be used with
+@samp{--create}.
+
+@menu
+* Ignore Failed Read::
+@end menu
+
+@node Ignore Failed Read
+@subsection Ignore Fail Read
+
+@table @kbd
+@item --ignore-failed-read
+Do not exit with nonzero on unreadable files or directories.
+@end table
+
+@node extract options
@section Options Used by @code{--extract}
@UNREVISED
there's a better way of organizing them.}
The previous chapter showed how to use @value{op-extract} to extract
-an archive into the filesystem. Various options cause @code{tar} to
+an archive into the filesystem. Various options cause @command{tar} to
extract more information than just file contents, such as the owner,
the permissions, the modification date, and so forth. This section
presents options to be used with @samp{--extract} when certain special
@menu
* Reading:: Options to Help Read Archives
-* Writing:: Changing How @code{tar} Writes Files
+* Writing:: Changing How @command{tar} Writes Files
* Scarce:: Coping with Scarce Resources
@end menu
-@node Reading, Writing, extract options, extract options
+@node Reading
@subsection Options to Help Read Archives
@cindex Options when reading archives
@cindex Reading incomplete records
@cindex Running out of space
@UNREVISED
-Normally, @code{tar} will request data in full record increments from
+Normally, @command{tar} will request data in full record increments from
an archive storage device. If the device cannot return a full record,
-@code{tar} will report an error. However, some devices do not always
+@command{tar} will report an error. However, some devices do not always
return full records, or do not require the last record of an archive to
be padded out to the next record boundary. To keep reading until you
obtain a full record, or to accept an incomplete record if it contains
@value{xref-read-full-records}.
The @value{op-read-full-records} option is turned on by default when
-@code{tar} reads an archive from standard input, or from a remote
+@command{tar} reads an archive from standard input, or from a remote
machine. This is because on BSD Unix systems, attempting to read a
pipe returns however much happens to be in the pipe, even if it is
-less than was requested. If this option were not enabled, @code{tar}
+less than was requested. If this option were not enabled, @command{tar}
would fail as soon as it read an incomplete record from the pipe.
If you're not sure of the blocking factor of an archive, you can
@menu
* read full records::
* Ignore Zeros::
-* Ignore Failed Read::
@end menu
-@node read full records, Ignore Zeros, Reading, Reading
+@node read full records
@unnumberedsubsubsec Reading Full Records
@FIXME{need sentence or so of intro here}
than the one specified.
@end table
-@node Ignore Zeros, Ignore Failed Read, read full records, Reading
+@node Ignore Zeros
@unnumberedsubsubsec Ignoring Blocks of Zeros
-Normally, @code{tar} stops reading when it encounters a block of zeros
+Normally, @command{tar} stops reading when it encounters a block of zeros
between file entries (which usually indicates the end of the archive).
-@value{op-ignore-zeros} allows @code{tar} to completely read an archive
+@value{op-ignore-zeros} allows @command{tar} to completely read an archive
which contains a block of zeros before the end (i.e.@: a damaged
-archive, or one which was created by @code{cat}-ing several archives
+archive, or one which was created by concatenating several archives
together).
The @value{op-ignore-zeros} option is turned off by default because many
-versions of @code{tar} write garbage after the end-of-archive entry,
-since that part of the media is never supposed to be read. GNU
-@code{tar} does not write after the end of an archive, but seeks to
+versions of @command{tar} write garbage after the end-of-archive entry,
+since that part of the media is never supposed to be read. @sc{gnu}
+@command{tar} does not write after the end of an archive, but seeks to
maintain compatiblity among archiving utilities.
@table @kbd
@value{op-extract} or @value{op-list}.
@end table
-@node Ignore Failed Read, , Ignore Zeros, Reading
-@unnumberedsubsubsec Ignore Fail Read
-
-@FIXME{Is this in the right place? It doesn't exist anywhere else in
-the book (except the appendix), and has no further explanation. For that
-matter, what does it mean?!}
-
-@table @kbd
-@item --ignore-failed-read
-Do not exit with nonzero on unreadable files or directories.
-@end table
-
-@node Writing, Scarce, Reading, extract options
-@subsection Changing How @code{tar} Writes Files
+@node Writing
+@subsection Changing How @command{tar} Writes Files
@cindex Overwriting old files, prevention
@cindex Protecting old files
@cindex Modification times of extracted files
* remove files::
@end menu
-@node Prevention Overwriting, Keep Old Files, Writing, Writing
+@node Prevention Overwriting
@unnumberedsubsubsec Options to Prevent Overwriting Files
-Normally, @code{tar} writes extracted files into the file system without
+Normally, @command{tar} writes extracted files into the file system without
regard to the files already on the system; i.e., files with the same
names as archive members are overwritten when the archive is extracted.
If the name of a corresponding file name is a symbolic link, the file
empty directories and even symbolic links are automatically removed if
they are found to be on the way of the proper extraction.
-To prevent @code{tar} from extracting an archive member from an archive
+To prevent @command{tar} from extracting an archive member from an archive
if doing so will overwrite a file in the file system, use
@value{op-keep-old-files} in conjunction with @samp{--extract}. When
-this option is specified, @code{tar} will report an error stating the
+this option is specified, @command{tar} will report an error stating the
name of the files in conflict instead of overwriting the file with the
corresponding extracted archive member.
with the extraction, the existing file is not overwritten and preserved.
@FIXME{huh?} If you specify the @value{op-recursive-unlink} option,
-@code{tar} removes @emph{anything} that keeps you from extracting a file
+@command{tar} removes @emph{anything} that keeps you from extracting a file
as far as current permissions will allow it. This could include removal
of the contents of a full directory hierarchy. For example, someone
using this feature may be very surprised at the results when extracting
* Recursive Unlink::
@end menu
-@node Keep Old Files, Unlink First, Prevention Overwriting, Writing
+@node Keep Old Files
@unnumberedsubsubsec Keep Old Files
@table @kbd
@item --keep-old-files
@itemx -k
Do not overwrite existing files from archive. The
-@value{op-keep-old-files} option prevents @code{tar} from over-writing
+@value{op-keep-old-files} option prevents @command{tar} from over-writing
existing files with files with the same name from the archive.
The @value{op-keep-old-files} option is meaningless with @value{op-list}.
-Prevents @code{tar} from overwriting files in the file system during
+Prevents @command{tar} from overwriting files in the file system during
extraction.
@end table
-@node Unlink First, Recursive Unlink, Keep Old Files, Writing
+@node Unlink First
@unnumberedsubsubsec Unlink First
@table @kbd
overwrite them.
@end table
-@node Recursive Unlink, Modification Times, Unlink First, Writing
+@node Recursive Unlink
@unnumberedsubsubsec Recursive Unlink
@table @kbd
before extracting over them. @emph{This is a dangerous option!}
@end table
-Some people argue that GNU @code{tar} should not hesitate to overwrite
-files with other files when extracting. When extracting a @code{tar}
+Some people argue that @sc{gnu} @command{tar} should not hesitate to overwrite
+files with other files when extracting. When extracting a @command{tar}
archive, they expect to see a faithful copy of the state of the filesystem
when the archive was created. It is debatable that this would always
be a proper behavior. For example, suppose one has an archive in
which @file{usr/local} is a link to @file{usr/local2}. Since then,
maybe the site removed the link and renamed the whole hierarchy from
@file{/usr/local2} to @file{/usr/local}. Such things happen all the time.
-I guess it would not be welcome at all that GNU @code{tar} removes the
+I guess it would not be welcome at all that @sc{gnu} @command{tar} removes the
whole hierarchy just to make room for the link to be reinstated (unless it
@emph{also} simultaneously restores the full @file{/usr/local2}, of course!
-GNU @code{tar} is indeed able to remove a whole hierarchy to reestablish a
+@sc{gnu} @command{tar} is indeed able to remove a whole hierarchy to reestablish a
symbolic link, for example, but @emph{only if} @value{op-recursive-unlink}
is specified to allow this behavior. In any case, single files are
silently removed.
-@node Modification Times, Setting Access Permissions, Recursive Unlink, Writing
+@node Modification Times
@unnumberedsubsubsec Setting Modification Times
-Normally, @code{tar} sets the modification times of extracted files to
+Normally, @command{tar} sets the modification times of extracted files to
the modification times recorded for the files in the archive, but
limits the permissions of extracted files by the current @code{umask}
setting.
Use in conjunction with @value{op-extract}.
@end table
-@node Setting Access Permissions, Writing to Standard Output, Modification Times, Writing
+@node Setting Access Permissions
@unnumberedsubsubsec Setting Access Permissions
To set the modes (access permissions) of extracted files to those
files together, why is this useful. is it really useful with
more than one file?}
-@node Writing to Standard Output, remove files, Setting Access Permissions, Writing
+@node Writing to Standard Output
@unnumberedsubsubsec Writing to Standard Output
To write the extracted files to the standard output, instead of
@itemx -O
Writes files to the standard output. Used in conjunction with
@value{op-extract}. Extract files to standard output. When this option
-is used, instead of creating the files specified, @code{tar} writes
+is used, instead of creating the files specified, @command{tar} writes
the contents of the files extracted to its standard output. This may
be useful if you are only extracting the files in order to send them
through a pipe. This option is meaningless with @value{op-list}.
the standard output? is this useful with more that one file? Are
pipes the real reason?}
-@node remove files, , Writing to Standard Output, Writing
+@node remove files
@unnumberedsubsubsec Removing Files
@FIXME{the various macros in the front of the manual think that this
Remove files after adding them to the archive.
@end table
-@node Scarce, , Writing, extract options
+@node Scarce
@subsection Coping with Scarce Resources
@cindex Middle of the archive, starting in the
@cindex Running out of space during extraction
* Same Order::
@end menu
-@node Starting File, Same Order, Scarce, Scarce
+@node Starting File
@unnumberedsubsubsec Starting File
@table @kbd
space, you can use @value{op-starting-file} to start extracting only
after member @var{name} of the archive. This assumes, of course, that
there is now free space, or that you are now extracting into a
-different file system. (You could also choose to suspend @code{tar},
+different file system. (You could also choose to suspend @command{tar},
remove unnecessary files from the file system, and then restart the
-same @code{tar} operation. In this case, @value{op-starting-file} is
+same @command{tar} operation. In this case, @value{op-starting-file} is
not necessary. @value{xref-incremental}, @value{xref-interactive},
and @value{ref-exclude}.)
-@node Same Order, , Starting File, Scarce
+@node Same Order
@unnumberedsubsubsec Same Order
@table @kbd
@FIXME{i think this explanation is lacking.}
-The @value{op-same-order} option tells @code{tar} that the list of file
+The @value{op-same-order} option tells @command{tar} that the list of file
names to be listed or extracted is sorted in the same order as the
files in the archive. This allows a large list of names to be used,
even on a small machine that would not otherwise be able to hold all
This option is probably never needed on modern computer systems.
-@node backup, Applications, extract options, operations
+@node backup
@section Backup options
@cindex backup options
-GNU @code{tar} offers options for making backups of files before writing
+@sc{gnu} @command{tar} offers options for making backups of files before writing
new versions. These options control the details of these backups.
They may apply to the archive itself before it is created or rewritten,
-as well as individual extracted members. Other GNU programs (@code{cp},
-@code{install}, @code{ln}, and @code{mv}, for example) offer similar
+as well as individual extracted members. Other @sc{gnu} programs (@command{cp},
+@command{install}, @command{ln}, and @command{mv}, for example) offer similar
options.
Backup options may prove unexpectedly useful when extracting archives
@table @samp
-@item --backup
+@item --backup[=@var{method}]
@opindex --backup
-@cindex backups, making
-Make backups of files that are about to be overwritten or removed.
+@vindex VERSION_CONTROL
+@cindex backups
+Back up files that are about to be overwritten or removed.
Without this option, the original versions are destroyed.
-@item --suffix=@var{suffix}
-@opindex --suffix
-@cindex backup suffix
-@vindex SIMPLE_BACKUP_SUFFIX
-Append @var{suffix} to each backup file made with @samp{-b}. If this
-option is not specified, the value of the @code{SIMPLE_BACKUP_SUFFIX}
-environment variable is used. And if @code{SIMPLE_BACKUP_SUFFIX} is not
-set, the default is @samp{~}, just as in Emacs.
-
-@item --version-control=@var{method}
-@opindex --version-control
-@vindex VERSION_CONTROL
-@cindex backup files, type made
-Use @var{method} to determine the type of backups made with @value{op-backup}.
-If this option is not specified, the value of the @code{VERSION_CONTROL}
-environment variable is used. And if @code{VERSION_CONTROL} is not set,
-the default backup type is @samp{existing}.
+Use @var{method} to determine the type of backups made.
+If @var{method} is not specified, use the value of the @env{VERSION_CONTROL}
+environment variable. And if @env{VERSION_CONTROL} is not set,
+use the @samp{existing} method.
@vindex version-control @r{Emacs variable}
This option corresponds to the Emacs variable @samp{version-control};
-the same values for @var{method} are accepted as in Emacs. This options
-also more descriptive name. The valid @var{method}s (unique
-abbreviations are accepted):
+the same values for @var{method} are accepted as in Emacs. This option
+also allows more descriptive names. The valid @var{method}s are:
@table @samp
@item t
@end table
+@item --suffix=@var{suffix}
+@opindex --suffix
+@cindex backup suffix
+@vindex SIMPLE_BACKUP_SUFFIX
+Append @var{suffix} to each backup file made with @samp{--backup}. If this
+option is not specified, the value of the @env{SIMPLE_BACKUP_SUFFIX}
+environment variable is used. And if @env{SIMPLE_BACKUP_SUFFIX} is not
+set, the default is @samp{~}, just as in Emacs.
+
@end table
Some people express the desire to @emph{always} use the @var{op-backup}
option, by defining some kind of alias or script. This is not as easy
-as one may thing, due to the fact old style options should appear first
+as one may think, due to the fact that old style options should appear first
and consume arguments a bit unpredictably for an alias or script. But,
if you are ready to give up using old style options, you may resort to
using something like (a Bourne shell function here):
tar () @{ /usr/local/bin/tar --backup $*; @}
@end example
-@node Applications, looking ahead, backup, operations
-@section Notable @code{tar} Usages
+@node Applications
+@section Notable @command{tar} Usages
@UNREVISED
@FIXME{Using Unix file linking capability to recreate directory
structures---linking files into one subdirectory and then
-@code{tar}ring that directory.}
+@command{tar}ring that directory.}
@FIXME{Nice hairy example using absolute-names, newer, etc.}
computer system, transfer the archive to another system, and extract
the contents there. The basic transfer medium might be magnetic tape,
Internet FTP, or even electronic mail (though you must encode the
-archive with @code{uuencode} in order to transport it properly by
+archive with @command{uuencode} in order to transport it properly by
mail). Both machines do not have to use the same operating system, as
-long as they both support the @code{tar} program.
+long as they both support the @command{tar} program.
For example, here is how you might copy a directory's contents from
one disk to another, while preserving the dates, modes, owners and
@end smallexample
@noindent
-This is one of the easiest methods to transfer a @code{tar} archive.
+This is one of the easiest methods to transfer a @command{tar} archive.
-@node looking ahead, , Applications, operations
+@node looking ahead
@section Looking Ahead: The Rest of this Manual
You have now seen how to use all eight of the operations available to
-@code{tar}, and a number of the possible options. The next chapter
+@command{tar}, and a number of the possible options. The next chapter
explains how to choose and change file and archive names, how to use
files to store names of other files which you can then call as
-arguments to @code{tar} (this can help you save time if you expect to
+arguments to @command{tar} (this can help you save time if you expect to
archive the same list of files a number of times), and so forth.
@FIXME{in case it's not obvious, i'm making this up in some sense
based on my imited memory of what the next chapter *really* does. i
remember to sitck it in here. :-)}
If there are too many files to conveniently list on the command line,
-you can list the names in a file, and @code{tar} will read that file.
+you can list the names in a file, and @command{tar} will read that file.
@value{xref-files-from}.
-There are various ways of causing @code{tar} to skip over some files,
+There are various ways of causing @command{tar} to skip over some files,
and not archive them. @xref{Choosing}.
-@node Backups, Choosing, operations, Top
+@node Backups
@chapter Performing Backups and Restoring Files
@UNREVISED
-GNU @code{tar} is distributed along with the scripts which the Free
+@sc{gnu} @command{tar} is distributed along with the scripts which the Free
Software Foundation uses for performing backups. There is no corresponding
scripts available yet for doing restoration of files. Even if there is
a good chance those scripts may be satisfying to you, they are not the
@ifclear PUBLISH
Here is a possible plan for a future documentation about the backuping
-scripts which are provided within the GNU @code{tar} distribution.
+scripts which are provided within the @sc{gnu} @command{tar} distribution.
@example
.* dumps
@end ifclear
-This chapter documents both the provided FSF scripts and @code{tar}
+This chapter documents both the provided FSF scripts and @command{tar}
options which are more specific to usage as a backup tool.
To @dfn{back up} a file system means to create archives that contain
called @dfn{dumps}.
@menu
-* Full Dumps:: Using @code{tar} to Perform Full Dumps
-* Inc Dumps:: Using @code{tar} to Perform Incremental Dumps
+* Full Dumps:: Using @command{tar} to Perform Full Dumps
+* Inc Dumps:: Using @command{tar} to Perform Incremental Dumps
* incremental and listed-incremental:: The Incremental Options
* Backup Levels:: Levels of Backups
* Backup Parameters:: Setting Parameters for Backups and Restoration
* Scripted Restoration:: Using the Restore Script
@end menu
-@node Full Dumps, Inc Dumps, Backups, Backups
-@section Using @code{tar} to Perform Full Dumps
+@node Full Dumps
+@section Using @command{tar} to Perform Full Dumps
@UNREVISED
@cindex full dumps
@cindex corrupted archives
Full dumps should only be made when no other people or programs
are modifying files in the filesystem. If files are modified while
-@code{tar} is making the backup, they may not be stored properly in
+@command{tar} is making the backup, they may not be stored properly in
the archive, in which case you won't be able to restore them if you
have to. (Files not being modified are written with no trouble, and do
not corrupt the entire archive.)
Make sure you have enough tapes on hand to complete the backup.
If you want to dump each filesystem separately you will need to use
-the @value{op-one-file-system} option to prevent @code{tar} from crossing
+the @value{op-one-file-system} option to prevent @command{tar} from crossing
filesystem boundaries when storing (sub)directories.
The @value{op-incremental} option is not needed, since this is a complete
copy of everything in the filesystem, and a full restore from this
backup would only be done onto a completely empty disk.
-Unless you are in a hurry, and trust the @code{tar} program (and your
+Unless you are in a hurry, and trust the @command{tar} program (and your
tapes), it is a good idea to use the @value{op-verify} option, to make
sure your files really made it onto the dump properly. This will
also detect cases where the file was modified while (or just after)
@value{op-incremental} @FIXME{look it up}
-@value{op-incremental} handle old GNU-format incremental backup.
+@value{op-incremental} handle old @sc{gnu}-format incremental backup.
This option should only be used when creating an incremental backup of
-a filesystem. When the @value{op-incremental} option is used, @code{tar}
+a filesystem. When the @value{op-incremental} option is used, @command{tar}
writes, at the beginning of the archive, an entry for each of the
directories that will be operated on. The entry for a directory
includes a list of all the files in the directory at the time the
is going to be put in the archive. This information is used when
doing a complete incremental restore.
-Note that this option causes @code{tar} to create a non-standard
-archive that may not be readable by non-GNU versions of the @code{tar}
+Note that this option causes @command{tar} to create a non-standard
+archive that may not be readable by non-@sc{gnu} versions of the @command{tar}
program.
The @value{op-incremental} option means the archive is an incremental
backup. Its meaning depends on the command that it modifies.
-If the @value{op-incremental} option is used with @value{op-list}, @code{tar}
+If the @value{op-incremental} option is used with @value{op-list}, @command{tar}
will list, for each directory in the archive, the list of files in
that directory at the time the archive was created. This information
is put out in a format that is not easy for humans to read, but which
was made. If you don't use @value{op-incremental}, the file system will
probably fill up with files that shouldn't exist any more.
-@value{op-listed-incremental} handle new GNU-format incremental backup.
-This option handles new GNU-format incremental backup. It has much the
+@value{op-listed-incremental} handle new @sc{gnu}-format incremental backup.
+This option handles new @sc{gnu}-format incremental backup. It has much the
same effect as @value{op-incremental}, but also the time when the dump
is done and the list of directories dumped is written to the given
@var{file}. When restoring, only files newer than the saved time are
restored, and the directory list is used to speed up operations.
@value{op-listed-incremental} acts like @value{op-incremental}, but when
-used in conjunction with @value{op-create} will also cause @code{tar} to
+used in conjunction with @value{op-create} will also cause @command{tar} to
use the file @var{file}, which contains information about the state
of the filesystem at the time of the last backup, to decide which
files to include in the archive being created. That file will then
-be updated by @code{tar}. If the file @var{file} does not exist when
-this option is specified, @code{tar} will create it, and include all
+be updated by @command{tar}. If the file @var{file} does not exist when
+this option is specified, @command{tar} will create it, and include all
appropriate files in the archive.
The file, which is archive independent, contains the date it was last
modified and a list of devices, inode numbers and directory names.
-@code{tar} will archive files with newer mod dates or inode change
+@command{tar} will archive files with newer mod dates or inode change
times, and directories with an unchanged inode number and device but
a changed directory name. The file is updated after the files to
be archived are determined, but before the new archive is actually
created.
-GNU @code{tar} actually writes the file twice: once before the data
+@sc{gnu} @command{tar} actually writes the file twice: once before the data
and written, and once after.
-@node Inc Dumps, incremental and listed-incremental, Full Dumps, Backups
-@section Using @code{tar} to Perform Incremental Dumps
+@node Inc Dumps
+@section Using @command{tar} to Perform Incremental Dumps
@UNREVISED
@cindex incremental dumps
block size to be a multiple of 1 kB; for these devices, 126 is the
largest blocking factor that can be used.
-@node incremental and listed-incremental, Backup Levels, Inc Dumps, Backups
+@node incremental and listed-incremental
@section The Incremental Options
@UNREVISED
@value{op-listed-incremental}, which is described below.
@value{op-incremental} in conjunction with @value{op-create} causes
-@code{tar} to write, at the beginning of the archive, an entry for
+@command{tar} to write, at the beginning of the archive, an entry for
each of the directories that will be archived. The entry for a
directory includes a list of all the files in the directory at the
time the archive was created and a flag for each file indicating
whether or not the file is going to be put in the archive.
-Note that this option causes @code{tar} to create a non-standard
-archive that may not be readable by non-GNU versions of the @code{tar}
+Note that this option causes @command{tar} to create a non-standard
+archive that may not be readable by non-@sc{gnu} versions of the @command{tar}
program.
@value{op-incremental} in conjunction with @value{op-extract} causes
-@code{tar} to read the lists of directory contents previously stored
+@command{tar} to read the lists of directory contents previously stored
in the archive, @emph{delete} files in the file system that did not
exist in their directories when the archive was created, and then
extract the files in the archive.
@value{op-incremental} isn't specified, the file system will probably
fill up with files that shouldn't exist any more.
-@value{op-incremental} in conjunction with @value{op-list}, causes
-@code{tar} to print, for each directory in the archive, the list of
+@value{op-incremental} in conjunction with @value{op-list} causes
+@command{tar} to print, for each directory in the archive, the list of
files in that directory at the time the archive was created. This
information is put out in a format that is not easy for humans to
read, but which is unambiguous for a program: each file name is
by an additional null and a newline to indicate the end of the data.
@value{op-listed-incremental} acts like @value{op-incremental}, but when
-used in conjunction with @value{op-create} will also cause @code{tar}
+used in conjunction with @value{op-create} will also cause @command{tar}
to use the file @var{snapshot-file}, which contains information about
the state of the file system at the time of the last backup, to decide
which files to include in the archive being created. That file will
-then be updated by @code{tar}. If the file @var{file} does not exist
-when this option is specified, @code{tar} will create it, and include
+then be updated by @command{tar}. If the file @var{file} does not exist
+when this option is specified, @command{tar} will create it, and include
all appropriate files in the archive.
The file @var{file}, which is archive independent, contains the date
it was last modified and a list of devices, inode numbers and
-directory names. @code{tar} will archive files with newer mod dates
+directory names. @command{tar} will archive files with newer mod dates
or inode change times, and directories with an unchanged inode number
and device but a changed directory name. The file is updated after
the files to be archived are determined, but before the new archive is
devices have non-dependable values when an automounter gets in the picture.
This led to a great deal of spurious redumping in incremental dumps,
so it is somewhat useless to compare two NFS devices numbers over time.
-So @code{tar} now considers all NFS devices as being equal when it comes
+So @command{tar} now considers all NFS devices as being equal when it comes
to comparing directories; this is fairly gross, but there does not seem
to be a better way to go.
@FIXME{this section needs to be written}
-@node Backup Levels, Backup Parameters, incremental and listed-incremental, Backups
+@node Backup Levels
@section Levels of Backups
@UNREVISED
files changed or created since the last daily backup. (Doing dumps
more than once a day is usually not worth the trouble).
-GNU @code{tar} comes with scripts you can use to do full and level-one
+@sc{gnu} @command{tar} comes with scripts you can use to do full and level-one
dumps. Using scripts (shell programs) to perform backups and
restoration is a convenient and reliable alternative to typing out
-file name lists and @code{tar} commands by hand.
+file name lists and @command{tar} commands by hand.
Before you use these scripts, you need to edit the file
@file{backup-specs}, which specifies parameters used by the backup
@FIXME{shorten node names}
-@node Backup Parameters, Scripted Backups, Backup Levels, Backups
+@node Backup Parameters
@section Setting Parameters for Backups and Restoration
@UNREVISED
The file @file{backup-specs} specifies backup parameters for the
-backup and restoration scripts provided with @code{tar}. You must
+backup and restoration scripts provided with @command{tar}. You must
edit @file{backup-specs} to fit your system configuration and schedule
before using these scripts.
to 23, or the string @samp{now}.
@item TAPE_FILE
-The device @code{tar} writes the archive to. This device should be
+The device @command{tar} writes the archive to. This device should be
attached to the host on which the dump scripts are run.
@FIXME{examples for all ...}
command; in that case, simply use `TAPE_STATUS=false'.
@item BLOCKING
-The blocking factor @code{tar} will use when writing the dump archive.
+The blocking factor @command{tar} will use when writing the dump archive.
@value{xref-blocking-factor}.
@item BACKUP_DIRS
included, regardless of how they may look to other networked machines.
Subdirectories on other file systems will be ignored.
-The host name specifies which host to run @code{tar} on, and should
+The host name specifies which host to run @command{tar} on, and should
normally be the host that actually contains the file system. However,
-the host machine must have GNU @code{tar} installed, and must be able
+the host machine must have @sc{gnu} @command{tar} installed, and must be able
to access the directory containing the backup scripts and their
support files using the same file name that is used on the machine
-where the scripts are run (ie. what @code{pwd} will print when in that
+where the scripts are run (ie. what @command{pwd} will print when in that
directory on that machine). If the host that contains the file system
does not have this capability, you can specify another host as long as
it can access the file system through NFS.
* Script Syntax:: Syntax for @file{Backup-specs}
@end menu
-@node backup-specs example, Script Syntax, Backup Parameters, Backup Parameters
+@node backup-specs example
@subsection An Example Text of @file{Backup-specs}
@UNREVISED
@end example
-@node Script Syntax, , backup-specs example, Backup Parameters
+@node Script Syntax
@subsection Syntax for @file{Backup-specs}
@UNREVISED
@file{backup-specs}, however, the parameters BACKUP_DIRS and
BACKUP_FILES can contain wildcards.
-@node Scripted Backups, Scripted Restoration, Backup Parameters, Backups
+@node Scripted Backups
@section Using the Backup Scripts
@UNREVISED
The script also prints the name of each system being dumped to the
standard output.
-@node Scripted Restoration, , Scripted Backups, Backups
+@node Scripted Restoration
@section Using the Restore Script
@UNREVISED
@ifset PUBLISH
-The @code{tar} distribution does not provide restoring scripts.
+The @command{tar} distribution does not provide restoring scripts.
@end ifset
@ifclear PUBLISH
@quotation
-@strong{Warning:} The GNU @code{tar} distribution does @emph{not}
+@strong{Warning:} The @sc{gnu} @command{tar} distribution does @emph{not}
provide any such @code{restore} script yet. This section is only
listed here for documentation maintenance purposes. In any case,
all contents is subject to change as things develop.
@end ifclear
-@node Choosing, Date input formats, Backups, Top
-@chapter Choosing Files and Names for @code{tar}
+@node Choosing
+@chapter Choosing Files and Names for @command{tar}
@UNREVISED
@FIXME{Melissa (still) Doesn't Really Like This ``Intro'' Paragraph!!!}
-Certain options to @code{tar} enable you to specify a name for your
+Certain options to @command{tar} enable you to specify a name for your
archive. Other options let you decide which files to include or exclude
from the archive, based on when or whether files were modified, whether
the file names do or don't match specified patterns, or whether files
* one:: Crossing Filesystem Boundaries
@end menu
-@node file, Selecting Archive Members, Choosing, Choosing
+@node file
@section Choosing and Naming Archive Files
@cindex Naming an archive
@cindex Archive Name
@FIXME{should the title of this section actually be, "naming an
archive"?}
-By default, @code{tar} uses an archive file name that was compiled when
+By default, @command{tar} uses an archive file name that was compiled when
it was built on the system; usually this name refers to some physical
-tape drive on the machine. However, the person who installed @code{tar}
+tape drive on the machine. However, the person who installed @command{tar}
on the system may not set the default to a meaningful value as far as
most users are concerned. As a result, you will usually want to tell
-@code{tar} where to find (or create) the archive. The @value{op-file}
+@command{tar} where to find (or create) the archive. The @value{op-file}
option allows you to either specify or name a file to use as the archive
instead of the default archive file location.
any operation.
@end table
-For example, in this @code{tar} command,
+For example, in this @command{tar} command,
@example
$ @kbd{tar -cvf collection.tar blues folk jazz}
follow the @samp{-f} option, since whatever directly follows @samp{-f}
@emph{will} end up naming the archive. If you neglect to specify an
archive name, you may end up overwriting a file in the working directory
-with the archive you create since @code{tar} will use this file's name
+with the archive you create since @command{tar} will use this file's name
for the archive name.
An archive can be saved as a file in the file system, sent through a
@cindex Writing new archives
@cindex Archive creation
-If you do not name the archive, @code{tar} uses the value of the
-environment variable @code{TAPE} as the file name for the archive. If
-that is not available, @code{tar} uses a default, compiled-in archive
+If you do not name the archive, @command{tar} uses the value of the
+environment variable @env{TAPE} as the file name for the archive. If
+that is not available, @command{tar} uses a default, compiled-in archive
name, usually that for tape unit zero (ie. @file{/dev/tu00}).
-@code{tar} always needs an archive name.
+@command{tar} always needs an archive name.
-If you use @file{-} as an @var{archive-name}, @code{tar} reads the
+If you use @file{-} as an @var{archive-name}, @command{tar} reads the
archive from standard input (when listing or extracting files), or
writes it to standard output (when creating an archive). If you use
@file{-} as an @var{archive-name} when modifying an archive,
-@code{tar} reads the original archive from its standard input and
+@command{tar} reads the original archive from its standard input and
writes the entire new archive to its standard output.
@FIXME{might want a different example here; this is already used in
@end example
@noindent
-@code{tar} will complete the remote connection, if possible, and
+@command{tar} will complete the remote connection, if possible, and
prompt you for a username and password. If you use
-@samp{--file=@@@var{hostname}:/@var{dev}/@var{file name}}, @code{tar}
+@samp{--file=@@@var{hostname}:/@var{dev}/@var{file name}}, @command{tar}
will complete the remote connection, if possible, using your username
as the username on the remote machine.
If the archive file name includes a colon (@samp{:}), then it is assumed
to be a file on another machine. If the archive file is
@samp{@var{user}@@@var{host}:@var{file}}, then @var{file} is used on the
-host @var{host}. The remote host is accessed using the @code{rsh}
+host @var{host}. The remote host is accessed using the @command{rsh}
program, with a username of @var{user}. If the username is omitted
(along with the @samp{@@} sign), then your user name will be used.
-(This is the normal @code{rsh} behavior.) It is necessary for the
-remote machine, in addition to permitting your @code{rsh} access, to
+(This is the normal @command{rsh} behavior.) It is necessary for the
+remote machine, in addition to permitting your @command{rsh} access, to
have the @file{/usr/ucb/rmt} program installed. If you need to use a
file whose name includes a colon, then the remote tape drive behavior
can be inhibited by using the @value{op-force-local} option.
here?>>. bob also comments that if Amanda isn't free software, we
shouldn't mention it..}
-When the archive is being created to @file{/dev/null}, GNU @code{tar}
+When the archive is being created to @file{/dev/null}, @sc{gnu} @command{tar}
tries to minimize input and output operations. The Amanda backup
-system, when used with GNU @code{tar}, has an initial sizing pass which
+system, when used with @sc{gnu} @command{tar}, has an initial sizing pass which
uses this feature.
-@node Selecting Archive Members, files, file, Choosing
+@node Selecting Archive Members
@section Selecting Archive Members
@cindex Specifying files to act on
@cindex Specifying archive members
@dfn{File Name arguments} specify which files in the file system
-@code{tar} operates on, when creating or adding to an archive, or which
-archive members @code{tar} operates on, when reading or deleting from
+@command{tar} operates on, when creating or adding to an archive, or which
+archive members @command{tar} operates on, when reading or deleting from
an archive. @xref{Operations}.
To specify file names, you can include them as the last arguments on
@end smallexample
If you specify a directory name as a file name argument, all the files
-in that directory are operated on by @code{tar}.
+in that directory are operated on by @command{tar}.
-If you do not specify files when @code{tar} is invoked with
-@value{op-create}, @code{tar} operates on all the non-directory files in
+If you do not specify files when @command{tar} is invoked with
+@value{op-create}, @command{tar} operates on all the non-directory files in
the working directory. If you specify either @value{op-list} or
-@value{op-extract}, @code{tar} operates on all the archive members in the
+@value{op-extract}, @command{tar} operates on all the archive members in the
archive. If you specify any operation other than one of these three,
-@code{tar} does nothing.
+@command{tar} does nothing.
-By default, @code{tar} takes file names from the command line. However,
+By default, @command{tar} takes file names from the command line. However,
there are other ways to specify file or member names, or to modify the
-manner in which @code{tar} selects the files or members upon which to
+manner in which @command{tar} selects the files or members upon which to
operate. @FIXME{add xref here}In general, these methods work both for
specifying the names of files and archive members.
-@node files, exclude, Selecting Archive Members, Choosing
+@node files
@section Reading Names from a File
@UNREVISED
@cindex File Name arguments, alternatives
Instead of giving the names of files or archive members on the command
line, you can put the names into a file, and then use the
-@value{op-files-from} option to @code{tar}. Give the name of the file
+@value{op-files-from} option to @command{tar}. Give the name of the file
which contains the list of files to include as the argument to
@samp{--files-from}. In the list, the file names should be separated by
newlines. You will frequently use this option when you have generated
-the list of files to archive with the @code{find} utility.
+the list of files to archive with the @command{find} utility.
@table @kbd
@item --files-from=@var{file name}
you specify either @samp{--files-from=-} or @samp{-T -}), then the file
names are read from standard input.
-Unless you are running @code{tar} with @samp{--create}, you can not use
+Unless you are running @command{tar} with @samp{--create}, you can not use
both @samp{--files-from=-} and @samp{--file=-} (@samp{-f -}) in the same
command.
@FIXME{add bob's example, from his message on 2-10-97}
-The following example shows how to use @code{find} to generate a list of
+The following example shows how to use @command{find} to generate a list of
files smaller than 400K in length and put that list into a file
called @file{small-files}. You can then use the @samp{-T} option to
-@code{tar} to specify the files from that file, @file{small-files}, to
+@command{tar} to specify the files from that file, @file{small-files}, to
create the archive @file{little.tgz}. (The @samp{-z} option to
-@code{tar} compresses the archive with @code{gzip}; @pxref{gzip} for
+@command{tar} compresses the archive with @command{gzip}; @pxref{gzip} for
more information.)
@example
* nul::
@end menu
-@node nul, , files, files
-@ifinfo
-@unnumberedsubsec @kbd{NUL} Terminated File Names
-@end ifinfo
+@node nul
+@subsection @kbd{NUL} Terminated File Names
@cindex File names, terminated by @kbd{NUL}
@cindex @kbd{NUL} terminated file names
terminate in a newline.
@end table
-The @samp{--null} option is just like the one in GNU @code{xargs} and
-@code{cpio}, and is useful with the @samp{-print0} predicate of GNU
-@code{find}. In @code{tar}, @samp{--null} also causes
+The @samp{--null} option is just like the one in @sc{gnu} @command{xargs} and
+@command{cpio}, and is useful with the @samp{-print0} predicate of @sc{gnu}
+@command{find}. In @command{tar}, @samp{--null} also causes
@value{op-directory} options to be treated as file names to archive, in
case there are any files out there called @file{-C}.
-This example shows how to use @code{find} to generate a list of files
+This example shows how to use @command{find} to generate a list of files
larger than 800K in length and put that list into a file called
-@file{long-files}. The @samp{-print0} option to @code{find} just just
+@file{long-files}. The @samp{-print0} option to @command{find} just just
like @samp{-print}, except that it separates files with a @kbd{NUL}
-rather than with a newline. You can then run @code{tar} with both the
-@samp{--null} and @samp{-T} options to specify that @code{tar} get the
+rather than with a newline. You can then run @command{tar} with both the
+@samp{--null} and @samp{-T} options to specify that @command{tar} get the
files from that file, @file{long-files}, to create the archive
-@file{big.tgz}. The @samp{--null} option to @code{tar} will cause
-@code{tar} to recognize the @kbd{NUL} separator between files.
+@file{big.tgz}. The @samp{--null} option to @command{tar} will cause
+@command{tar} to recognize the @kbd{NUL} separator between files.
@example
$ @kbd{find . -size +800 -print0 > long-files}
@FIXME{say anything else here to conclude the section?}
-@node exclude, Wildcards, files, Choosing
+@node exclude
@section Excluding Some Files
@cindex File names, excluding files by
@cindex Excluding files by name and pattern
@table @kbd
@item --exclude=@var{pattern}
-Causes @code{tar} to ignore files that match the @var{pattern}.
+Causes @command{tar} to ignore files that match the @var{pattern}.
@end table
@findex exclude
@table @kbd
@item --exclude-from=@var{file}
@itemx -X @var{file}
-Causes @code{tar} to ignore files that match the patterns listed in
+Causes @command{tar} to ignore files that match the patterns listed in
@var{file}.
@end table
@findex exclude-from
Use the @samp{--exclude-from=@var{file-of-patterns}} option to read a
-list of shell wildcards, one per line, from @var{file}; @code{tar} will
-ignore files matching those regular expressions. Thus if @code{tar} is
+list of shell wildcards, one per line, from @var{file}; @command{tar} will
+ignore files matching those regular expressions. Thus if @command{tar} is
called as @w{@samp{tar -c -X foo .}} and the file @file{foo} contains a
single line @file{*.o}, no files whose names end in @file{.o} will be
added to the archive.
* problems with exclude::
@end menu
-@node problems with exclude, , exclude, exclude
+@node problems with exclude
@unnumberedsubsec Problems with Using the @code{exclude} Options
Some users find @samp{exclude} options confusing. Here are some common
@itemize @bullet
@item
-The main operating mode of @code{tar} does not act on a path name
+The main operating mode of @command{tar} does not act on a path name
explicitly listed on the command line if one of its file name
components is excluded. In the example above, if
you create an archive and exclude files that end with @samp{*.o}, but
@item
When you use @value{op-exclude}, be sure to quote the @var{pattern}
-parameter, so GNU @code{tar} sees wildcard characters like @samp{*}.
+parameter, so @sc{gnu} @command{tar} sees wildcard characters like @samp{*}.
If you do not do this, the shell might expand the @samp{*} itself
-using files at hand, so @code{tar} might receive a list of files
+using files at hand, so @command{tar} might receive a list of files
instead of one pattern, or none at all, making the command somewhat
illegal. This might not correspond to what you want.
@item
You must use use shell syntax, or globbing, rather than @code{regexp}
-syntax, when using exclude options in @code{tar}. If you try to use
+syntax, when using exclude options in @command{tar}. If you try to use
@code{regexp} syntax to describe files to be excluded, your command
might fail.
@item
-In earlier versions of @code{tar}, what is now the
+In earlier versions of @command{tar}, what is now the
@samp{--exclude-from=@var{file-of-patterns}} option was called
@samp{--exclude-@var{pattern}} instead. Now,
@samp{--exclude=@var{pattern}} applies to patterns listed on the command
@end itemize
-@node Wildcards, after, exclude, Choosing
+@node Wildcards
@section Wildcards Patterns and Matching
@dfn{Globbing} is the operation by which @dfn{wildcard} characters,
@samp{*} or @samp{?} for example, are replaced and expanded into all
-existing files matching the given pattern. However, @code{tar} often
+existing files matching the given pattern. However, @command{tar} often
uses wildcard patterns for matching (or globbing) archive members instead
of actual files in the filesystem. Wildcard patterns are also used for
-verifying volume labels of @code{tar} archives. This section has the
-purpose of explaining wildcard syntax for @code{tar}.
+verifying volume labels of @command{tar} archives. This section has the
+purpose of explaining wildcard syntax for @command{tar}.
@FIXME{the next few paragraphs need work.}
string: excluding a directory also excludes all the files beneath it.
There are some discussions floating in the air and asking for modifications
-in the way GNU @code{tar} accomplishes wildcard matches. We perceive
+in the way @sc{gnu} @command{tar} accomplishes wildcard matches. We perceive
any change of semantics in this area as a delicate thing to impose on
-GNU @code{tar} users. On the other hand, the GNU project should be
+@sc{gnu} @command{tar} users. On the other hand, the @sc{gnu} project should be
progressive enough to correct any ill design: compatibility at all price
is not always a good attitude. In conclusion, it is @emph{possible}
that slight amendments be later brought to the previous description.
Your opinions on the matter are welcome.
-@node after, recurse, Wildcards, Choosing
+@node after
@section Operating Only on New Files
@cindex Excluding file by age
@cindex Modification time, excluding files by
@cindex Age, excluding files by
@UNREVISED
-The @value{op-after-date} option causes @code{tar} to only work on files
+The @value{op-after-date} option causes @command{tar} to only work on files
whose modification or inode-changed times are newer than the @var{date}
given. If you use this option when creating or appending to an archive,
the archive will only include new files. If you use @samp{--after-date}
-when extracting an archive, @code{tar} will only extract files newer
+when extracting an archive, @command{tar} will only extract files newer
than the @var{date} you specify.
-If you only want @code{tar} to make the date comparison based on
+If you only want @command{tar} to make the date comparison based on
modification of the actual contents of the file (rather than inode
changes), then use the @value{op-newer-mtime} option.
You may use these options with any operation. Note that these options
differ from the @value{op-update} operation in that they allow you to
-specify a particular date against which @code{tar} can compare when
+specify a particular date against which @command{tar} can compare when
deciding whether or not to archive the files.
@table @kbd
Acts like @value{op-after-date}, but only looks at modification times.
@end table
-These options limit @code{tar} to only operating on files which have
+These options limit @command{tar} to only operating on files which have
been modified after the date specified. A file is considered to have
changed if the contents have been modified, or if the owner,
permissions, and so forth, have been changed. (For more information on
@end quotation
To select files newer than the modification time of a file that already
-exists, you can use the @samp{--reference} (@samp{-r}) option of GNU
-@code{date}, available in GNU shell utilities 1.13 or later. It returns
+exists, you can use the @samp{--reference} (@samp{-r}) option of @sc{gnu}
+@command{date}, available in @sc{gnu} shell utilities 1.13 or later. It returns
the time stamp of the already-existing file; this time stamp expands to
become the referent date which @samp{--newer} uses to determine which
files to archive. For example, you could say,
@noindent
@FIXME{which tells -- need to fill this in!}
-@node recurse, one, after, Choosing
+@node recurse
@section Descending into Directories
@cindex Avoiding recursion in directories
@cindex Descending directories, avoiding
@FIXME{show dan bob's comments, from 2-10-97}
-Usually, @code{tar} will recursively explore all directories (either
+Usually, @command{tar} will recursively explore all directories (either
those given on the command line or through the @value{op-files-from}
option) for the various files they contain. However, you may not always
-want @code{tar} to act this way.
+want @command{tar} to act this way.
-The @value{op-no-recursion} option inhibits @code{tar}'s recursive descent
+The @value{op-no-recursion} option inhibits @command{tar}'s recursive descent
into specified directories. If you specify @samp{--no-recursion}, you can
-use the @code{find} utility for hunting through levels of directories to
-construct a list of file names which you could then pass to @code{tar}.
-@code{find} allows you to be more selective when choosing which files to
-archive; see @ref{files} for more information on using @code{find} with
-@code{tar}, or look.
+use the @command{find} utility for hunting through levels of directories to
+construct a list of file names which you could then pass to @command{tar}.
+@command{find} allows you to be more selective when choosing which files to
+archive; see @ref{files} for more information on using @command{find} with
+@command{tar}, or look.
@table @kbd
@item --no-recursion
-Prevents @code{tar} from recursively descending directories.
+Prevents @command{tar} from recursively descending directories.
@end table
-When you use @samp{--no-recursion}, GNU @code{tar} grabs directory entries
+When you use @samp{--no-recursion}, @sc{gnu} @command{tar} grabs directory entries
themselves, but does not descend on them recursively. Many people use
-@code{find} for locating files they want to back up, and since
-@code{tar} @emph{usually} recursively descends on directories, they have
-to use the @samp{@w{! -d}} option to @code{find} @FIXME{needs more
+@command{find} for locating files they want to back up, and since
+@command{tar} @emph{usually} recursively descends on directories, they have
+to use the @samp{@w{! -d}} option to @command{find} @FIXME{needs more
explanation or a cite to another info file}as they usually do not want
all the files in a directory. They then use the @value{op-file-from}
-option to archive the files located via @code{find}.
+option to archive the files located via @command{find}.
The problem when restoring files archived in this manner is that the
directories themselves are not in the archive; so the
@value{op-same-permissions} option does not affect them---while users
might really like it to. Specifying @value{op-no-recursion} is a way to
-tell @code{tar} to grab only the directory entries given to it, adding
+tell @command{tar} to grab only the directory entries given to it, adding
no new files on its own.
@FIXME{example here}
-@node one, , recurse, Choosing
+@node one
@section Crossing Filesystem Boundaries
@cindex File system boundaries, not crossing
@UNREVISED
-@code{tar} will normally automatically cross file system boundaries in
+@command{tar} will normally automatically cross file system boundaries in
order to archive files which are part of a directory tree. You can
-change this behavior by running @code{tar} and specifying
+change this behavior by running @command{tar} and specifying
@value{op-one-file-system}. This option only affects files that are
archived because they are in a directory that is being archived;
-@code{tar} will still archive files explicitly named on the command line
+@command{tar} will still archive files explicitly named on the command line
or through @value{op-files-from}, regardless of where they reside.
@table @kbd
@item --one-file-system
@itemx -l
-Prevents @code{tar} from crossing file system boundaries when
+Prevents @command{tar} from crossing file system boundaries when
archiving. Use in conjunction with any write operation.
@end table
-The @samp{--one-file-system} option causes @code{tar} to modify its
+The @samp{--one-file-system} option causes @command{tar} to modify its
normal behavior in archiving the contents of directories. If a file in
a directory is not on the same filesystem as the directory itself, then
-@code{tar} will not archive that file. If the file is a directory
-itself, @code{tar} will not archive anything beneath it; in other words,
-@code{tar} will not cross mount points.
+@command{tar} will not archive that file. If the file is a directory
+itself, @command{tar} will not archive anything beneath it; in other words,
+@command{tar} will not cross mount points.
It is reported that using this option, the mount point is is archived,
but nothing under it.
* absolute:: Absolute File Names
@end menu
-@node directory, absolute, one, one
+@node directory
@subsection Changing the Working Directory
@FIXME{need to read over this node now for continuity; i've switched
Note that @samp{--directory} options are interpreted consecutively. If
@samp{--directory} specifies a relative file name, it is interpreted
relative to the then current directory, which might not be the same as
-the original current working directory of @code{tar}, due to a previous
+the original current working directory of @command{tar}, due to a previous
@samp{--directory} option.
@FIXME{dan: does this mean that you *can* use the short option form, but
@samp{--directory} options in the file list. (This interpretation can
be disabled by using the @value{op-null} option.)
-@node absolute, , directory, one
+@node absolute
@subsection Absolute File Names
@UNREVISED
Do not strip leading slashes from file names.
@end table
-By default, GNU @code{tar} drops a leading @samp{/} on input or output.
+By default, @sc{gnu} @command{tar} drops a leading @samp{/} on input or output.
This option turns off this behavior.
Tt is roughly equivalent to changing to the
-root directory before running @code{tar} (except it also turns off the
+root directory before running @command{tar} (except it also turns off the
usual warning message).
-When @code{tar} extracts archive members from an archive, it strips any
+When @command{tar} extracts archive members from an archive, it strips any
leading slashes (@samp{/}) from the member name. This causes absolute
member names in the archive to be treated as relative file names. This
allows you to have such members extracted wherever you want, instead of
being restricted to extracting the member in the exact directory named
in the archive. For example, if the archive member has the name
-@file{/etc/passwd}, @code{tar} will extract it as if the name were
+@file{/etc/passwd}, @command{tar} will extract it as if the name were
really @file{etc/passwd}.
-Other @code{tar} programs do not do this. As a result, if you create an
+Other @command{tar} programs do not do this. As a result, if you create an
archive whose member names start with a slash, they will be difficult
-for other people with a non-GNU @code{tar} program to use. Therefore,
-GNU @code{tar} also strips leading slashes from member names when
-putting members into the archive. For example, if you ask @code{tar} to
+for other people with a non-@sc{gnu} @command{tar} program to use. Therefore,
+@sc{gnu} @command{tar} also strips leading slashes from member names when
+putting members into the archive. For example, if you ask @command{tar} to
add the file @file{/bin/ls} to an archive, it will do so, but the member
name will be @file{bin/ls}.
-If you use the @value{op-absolute-names} option, @code{tar} will do
+If you use the @value{op-absolute-names} option, @command{tar} will do
neither of these transformations.
To archive or extract files relative to the root directory, specify
the @value{op-absolute-names} option.
-Normally, @code{tar} acts on files relative to the working
+Normally, @command{tar} acts on files relative to the working
directory---ignoring superior directory names when archiving, and
ignoring leading slashes when extracting.
-When you specify @value{op-absolute-names}, @code{tar} stores file names
+When you specify @value{op-absolute-names}, @command{tar} stores file names
including all superior directory names, and preserves leading slashes.
-If you only invoked @code{tar} from the root directory you would never
+If you only invoked @command{tar} from the root directory you would never
need the @value{op-absolute-names} option, but using this option may be
more convenient than switching to root.
@FIXME{this is still horrible; need to talk with dan on monday.}
-@code{tar} prints out a message about removing the @samp{/} from file
-names. This message appears once per GNU @code{tar} invocation. It
+@command{tar} prints out a message about removing the @samp{/} from file
+names. This message appears once per @sc{gnu} @command{tar} invocation. It
represents something which ought to be told; ignoring what it means can
cause very serious surprises, later.
Some people, nevertheless, do not want to see this message. Wanting to
-play really dangerously, one may of course redirect @code{tar} standard
-error to the sink. For example, under @code{sh}:
+play really dangerously, one may of course redirect @command{tar} standard
+error to the sink. For example, under @command{sh}:
@example
$ @kbd{tar -c -f archive.tar /home 2> /dev/null}
$ @kbd{tar -c -f archive.tar -C / home}
@end example
-@node Date input formats, Formats, Choosing, Top
+@node Date input formats
@chapter Date input formats
@cindex date input formats
--- Robert Grudin, @cite{Time and the Art of Living}.
@end quotation
-This section describes the textual date representations that GNU
+This section describes the textual date representations that @sc{gnu}
programs accept. These are the strings you, as a user, can supply as
arguments to the various programs. The C interface (via the
@code{getdate} function) is not described here.
* General date syntax:: Common rules.
* Calendar date item:: 19 Dec 1994.
* Time of day item:: 9:20pm.
-* Time zone item:: EST, GMT, UTC, ...
+* Time zone item:: @sc{est}, @sc{gmt}, @sc{utc}, ...
* Day of week item:: Monday and others.
* Relative item in date strings:: next tuesday, 2 years ago.
* Pure numbers in date strings:: 19931219, 1440.
@end menu
-@node General date syntax, Calendar date item, Date input formats, Date input formats
+@node General date syntax
@section General date syntax
@cindex general date syntax
zeros on numbers are ignored.
-@node Calendar date item, Time of day item, General date syntax, Date input formats
+@node Calendar date item
@section Calendar date item
@cindex calendar date item
@end example
-@node Time of day item, Time zone item, Calendar date item, Date input formats
+@node Time of day item
@section Time of day item
@cindex time of day item
20:02:0
20:02
8:02pm
-20:02-0500 # In EST (U.S. Eastern Standard Time).
+20:02-0500 # In @sc{est} (U.S. Eastern Standard Time).
@end example
More generally, the time of the day may be given as
expressed as @samp{@var{s}@var{hh}@var{mm}}, where @var{s} is @samp{+}
or @samp{-}, @var{hh} is a number of zone hours and @var{mm} is a number
of zone minutes. When a time zone correction is given this way, it
-forces interpretation of the time in UTC, overriding any previous
+forces interpretation of the time in @sc{utc}, overriding any previous
specification for the time zone or the local time zone. The @var{minute}
part of the time of the day may not be elided when a time zone correction
is used.
but not both.
-@node Time zone item, Day of week item, Time of day item, Date input formats
+@node Time zone item
@section Time zone item
@cindex time zone item
unambiguous numeric time zone corrections like @samp{-0500}, as
described in the previous section.
-@node Day of week item, Relative item in date strings, Time zone item, Date input formats
+@node Day of week item
@section Day of week item
@cindex day of week item
A comma following a day of the week item is ignored.
-@node Relative item in date strings, Pure numbers in date strings, Day of week item, Date input formats
+@node Relative item in date strings
@section Relative item in date strings
@cindex relative items in date strings
to the local time.
-@node Pure numbers in date strings, Authors of getdate, Relative item in date strings, Date input formats
+@node Pure numbers in date strings
@section Pure numbers in date strings
@cindex pure numbers in date strings
year.
-@node Authors of getdate, , Pure numbers in date strings, Date input formats
+@node Authors of getdate
@section Authors of @code{getdate}
@cindex authors of @code{getdate}
at Chapel Hill. The code was later tweaked by a couple of people on
Usenet, then completely overhauled by Rich $alz (@samp{rsalz@@bbn.com})
and Jim Berets (@samp{jberets@@bbn.com}) in August, 1990. Various
-revisions for the GNU system were made by David MacKenzie, Jim Meyering,
+revisions for the @sc{gnu} system were made by David MacKenzie, Jim Meyering,
and others.
@cindex Pinard, F.
(@samp{pinard@@iro.umontreal.ca}) from the @file{getdate.y} source code,
and then edited by K.@: Berry (@samp{kb@@cs.umb.edu}).
-@node Formats, Media, Date input formats, Top
+@node Formats
@chapter Controlling the Archive Format
@FIXME{need an intro here}
@menu
-* Portability:: Making @code{tar} Archives More Portable
+* Portability:: Making @command{tar} Archives More Portable
* Compression:: Using Less Space through Compression
* Attributes:: Handling File Attributes
* Standard:: The Standard Format
-* Extensions:: GNU Extensions to the Archive Format
-* cpio:: Comparison of @code{tar} and @code{cpio}
+* Extensions:: @sc{gnu} Extensions to the Archive Format
+* cpio:: Comparison of @command{tar} and @command{cpio}
@end menu
-@node Portability, Compression, Formats, Formats
-@section Making @code{tar} Archives More Portable
+@node Portability
+@section Making @command{tar} Archives More Portable
-Creating a @code{tar} archive on a particular system that is meant to be
-useful later on many other machines and with other versions of @code{tar}
-is more challenging than you might think. @code{tar} archive formats
+Creating a @command{tar} archive on a particular system that is meant to be
+useful later on many other machines and with other versions of @command{tar}
+is more challenging than you might think. @command{tar} archive formats
have been evolving since the first versions of Unix. Many such formats
are around, and are not always compatible with each other. This section
-discusses a few problems, and gives some advice about making @code{tar}
+discusses a few problems, and gives some advice about making @command{tar}
archives more portable.
-One golden rule is simplicity. For example, limit your @code{tar}
+One golden rule is simplicity. For example, limit your @command{tar}
archives to contain only regular files and directories, avoiding
other kind of special files. Do not attempt to save sparse files or
contiguous files as such. Let's discuss a few more problems, in turn.
* Portable Names:: Portable Names
* dereference:: Symbolic Links
* old:: Old V7 Archives
-* posix:: POSIX archives
+* posix:: @sc{posix} archives
* Checksumming:: Checksumming Problems
+* Large or Negative Values:: Large files, negative time stamps, etc.
@end menu
-@node Portable Names, dereference, Portability, Portability
+@node Portable Names
@subsection Portable Names
Use portable file and member names. A name is portable if it contains
old Unix hosts, limit your file name components to 14 characters or
less.
-If you intend to have your @code{tar} archives to be read under MSDOS,
+If you intend to have your @command{tar} archives to be read under MSDOS,
you should not rely on case distinction for file names, and you might
-use the GNU @code{doschk} program for helping you further diagnosing
+use the @sc{gnu} @command{doschk} program for helping you further diagnosing
illegal MSDOS names, which are even more limited than System V's.
-@node dereference, old, Portable Names, Portability
+@node dereference
@subsection Symbolic Links
@cindex File names, using symbolic links
@cindex Symbolic link as file name
-Normally, when @code{tar} archives a symbolic link, it writes a
+Normally, when @command{tar} archives a symbolic link, it writes a
block to the archive naming the target of the link. In that way, the
-@code{tar} archive is a faithful record of the filesystem contents.
-@value{op-dereference} is used with @value{op-create}, and causes @code{tar}
+@command{tar} archive is a faithful record of the filesystem contents.
+@value{op-dereference} is used with @value{op-create}, and causes @command{tar}
to archive the files symbolic links point to, instead of the links
-themselves. When this option is used, when @code{tar} encounters a
+themselves. When this option is used, when @command{tar} encounters a
symbolic link, it will archive the linked-to file, instead of simply
recording the presence of a symbolic link.
The name under which the file is stored in the file system is not
recorded in the archive. To record both the symbolic link name and
the file name in the system, archive the file under both names. If
-all links were recorded automatically by @code{tar}, an extracted file
+all links were recorded automatically by @command{tar}, an extracted file
might be linked to a file name that no longer exists in the file
system.
-If a linked-to file is encountered again by @code{tar} while creating
+If a linked-to file is encountered again by @command{tar} while creating
the same archive, an entire second copy of it will be stored. (This
@emph{might} be considered a bug.)
symbolic links, and moreover, your distribution might be unusable if
it contains unresolved symbolic links.
-@node old, posix, dereference, Portability
+@node old
@subsection Old V7 Archives
@cindex Format, old style
@cindex Old style format
@cindex Old style archives
-Certain old versions of @code{tar} cannot handle additional
-information recorded by newer @code{tar} programs. To create an
+Certain old versions of @command{tar} cannot handle additional
+information recorded by newer @command{tar} programs. To create an
archive in V7 format (not ANSI), which can be read by these old
versions, specify the @value{op-old-archive} option in
-conjunction with the @value{op-create}. @code{tar} also
+conjunction with the @value{op-create}. @command{tar} also
accepts @samp{--portability} for this option. When you specify it,
-@code{tar} leaves out information about directories, pipes, fifos,
+@command{tar} leaves out information about directories, pipes, fifos,
contiguous files, and device files, and specifies file ownership by
group and user IDs instead of group and user names.
unless the archive was created with using this option.
In most cases, a @emph{new} format archive can be read by an @emph{old}
-@code{tar} program without serious trouble, so this option should
-seldom be needed. On the other hand, most modern @code{tar}s are
+@command{tar} program without serious trouble, so this option should
+seldom be needed. On the other hand, most modern @command{tar}s are
able to read old format archives, so it might be safer for you to
always use @value{op-old-archive} for your distributions.
-@node posix, Checksumming, old, Portability
-@subsection GNU @code{tar} and POSIX @code{tar}
+@node posix
+@subsection @sc{gnu} @command{tar} and @sc{posix} @command{tar}
-GNU @code{tar} was based on an early draft of the POSIX 1003.1
-@code{ustar} standard. GNU extensions to @code{tar}, such as the
+@sc{gnu} @command{tar} was based on an early draft of the @sc{posix} 1003.1
+@code{ustar} standard. @sc{gnu} extensions to @command{tar}, such as the
support for file names longer than 100 characters, use portions of the
-@code{tar} header record which were specified in that POSIX draft as
-unused. Subsequent changes in POSIX have allocated the same parts of
-the header record for other purposes. As a result, GNU @code{tar} is
-incompatible with the current POSIX spec, and with @code{tar} programs
+@command{tar} header record which were specified in that @sc{posix} draft as
+unused. Subsequent changes in @sc{posix} have allocated the same parts of
+the header record for other purposes. As a result, @sc{gnu} @command{tar} is
+incompatible with the current @sc{posix} spec, and with @command{tar} programs
that follow it.
-We plan to reimplement these GNU extensions in a new way which is
-upward compatible with the latest POSIX @code{tar} format, but we
+We plan to reimplement these @sc{gnu} extensions in a new way which is
+upward compatible with the latest @sc{posix} @command{tar} format, but we
don't know when this will be done.
In the mean time, there is simply no telling what might happen if you
-read a GNU @code{tar} archive, which uses the GNU extensions, using
-some other @code{tar} program. So if you want to read the archive
-with another @code{tar} program, be sure to write it using the
+read a @sc{gnu} @command{tar} archive, which uses the @sc{gnu} extensions, using
+some other @command{tar} program. So if you want to read the archive
+with another @command{tar} program, be sure to write it using the
@samp{--old-archive} option (@samp{-o}).
@FIXME{is there a way to tell which flavor of tar was used to write a
particular archive before you try to read it?}
-Traditionally, old @code{tar}s have a limit of 100 characters. GNU
-@code{tar} attempted two different approaches to overcome this limit,
+Traditionally, old @command{tar}s have a limit of 100 characters. @sc{gnu}
+@command{tar} attempted two different approaches to overcome this limit,
using and extending a format specified by a draft of some P1003.1.
The first way was not that successful, and involved @file{@@MaNgLeD@@}
file names, or such; while a second approach used @file{././@@LongLink}
-and other tricks, yielding better success. In theory, GNU @code{tar}
+and other tricks, yielding better success. In theory, @sc{gnu} @command{tar}
should be able to handle file names of practically unlimited length.
-So, if GNU @code{tar} fails to dump and retrieve files having more
-than 100 characters, then there is a bug in GNU @code{tar}, indeed.
+So, if @sc{gnu} @command{tar} fails to dump and retrieve files having more
+than 100 characters, then there is a bug in @sc{gnu} @command{tar}, indeed.
-But, being strictly POSIX, the limit was still 100 characters.
-For various other purposes, GNU @code{tar} used areas left unassigned
-in the POSIX draft. POSIX later revised P1003.1 @code{ustar} format by
+But, being strictly @sc{posix}, the limit was still 100 characters.
+For various other purposes, @sc{gnu} @command{tar} used areas left unassigned
+in the @sc{posix} draft. @sc{posix} later revised P1003.1 @code{ustar} format by
assigning previously unused header fields, in such a way that the upper
limit for file name length was raised to 256 characters. However, the
-actual POSIX limit oscillates between 100 and 256, depending on the
+actual @sc{posix} limit oscillates between 100 and 256, depending on the
precise location of slashes in full file name (this is rather ugly).
-Since GNU @code{tar} use the same fields for quite other purposes,
-it became incompatible with the latest POSIX standards.
+Since @sc{gnu} @command{tar} use the same fields for quite other purposes,
+it became incompatible with the latest @sc{posix} standards.
For longer or non-fitting file names, we plan to use yet another set
-of GNU extensions, but this time, complying with the provisions POSIX
+of @sc{gnu} extensions, but this time, complying with the provisions @sc{posix}
offers for extending the format, rather than conflicting with it.
-Whenever an archive uses old GNU @code{tar} extension format or POSIX
+Whenever an archive uses old @sc{gnu} @command{tar} extension format or @sc{posix}
extensions, would it be for very long file names or other specialities,
-this archive becomes non-portable to other @code{tar} implementations.
-In fact, anything can happen. The most forgiving @code{tar}s will
+this archive becomes non-portable to other @command{tar} implementations.
+In fact, anything can happen. The most forgiving @command{tar}s will
merely unpack the file using a wrong name, and maybe create another
file named something like @file{@@LongName}, with the true file name
-in it. @code{tar}s not protecting themselves may segment violate!
+in it. @command{tar}s not protecting themselves may segment violate!
Compatibility concerns make all this thing more difficult, as we
will have to support @emph{all} these things together, for a while.
-GNU @code{tar} should be able to produce and read true POSIX format
-files, while being able to detect old GNU @code{tar} formats, besides
+@sc{gnu} @command{tar} should be able to produce and read true @sc{posix} format
+files, while being able to detect old @sc{gnu} @command{tar} formats, besides
old V7 format, and process them conveniently. It would take years
before this whole area stabilizes@dots{}
-There are plans to raise this 100 limit to 256, and yet produce POSIX
-conforming archives. Past 256, I do not know yet if GNU @code{tar}
-will go non-POSIX again, or merely refuse to archive the file.
+There are plans to raise this 100 limit to 256, and yet produce @sc{posix}
+conforming archives. Past 256, I do not know yet if @sc{gnu} @command{tar}
+will go non-@sc{posix} again, or merely refuse to archive the file.
-There are plans so GNU @code{tar} support more fully the latest POSIX
-format, while being able to read old V7 format, GNU (semi-POSIX plus
-extension), as well as full POSIX. One may ask if there is part of
-the POSIX format that we still cannot support. This simple question
+There are plans so @sc{gnu} @command{tar} support more fully the latest @sc{posix}
+format, while being able to read old V7 format, @sc{gnu} (semi-@sc{posix} plus
+extension), as well as full @sc{posix}. One may ask if there is part of
+the @sc{posix} format that we still cannot support. This simple question
has a complex answer. Maybe that, on intimate look, some strong
limitations will pop up, but until now, nothing sounds too difficult
-(but see below). I only have these few pages of POSIX telling about
+(but see below). I only have these few pages of @sc{posix} telling about
`Extended tar Format' (P1003.1-1990 -- section 10.1.1), and there are
references to other parts of the standard I do not have, which should
normally enforce limitations on stored file names (I suspect things
some points which the standard does not make clear, Existing practice
will then drive what I should do.
-POSIX mandates that, when a file name cannot fit within 100 to
+@sc{posix} mandates that, when a file name cannot fit within 100 to
256 characters (the variance comes from the fact a @kbd{/} is
ideally needed as the 156'th character), or a link name cannot
fit within 100 characters, a warning should be issued and the file
@emph{not} be stored. Unless some @value{op-posix} option is given
-(or @code{POSIXLY_CORRECT} is set), I suspect that GNU @code{tar}
+(or @env{POSIXLY_CORRECT} is set), I suspect that @sc{gnu} @command{tar}
should disobey this specification, and automatically switch to using
-GNU extensions to overcome file name or link name length limitations.
+@sc{gnu} extensions to overcome file name or link name length limitations.
There is a problem, however, which I did not intimately studied yet.
-Given a truly POSIX archive with names having more than 100 characters,
-I guess that GNU @code{tar} up to 1.11.8 will process it as if it were an
+Given a truly @sc{posix} archive with names having more than 100 characters,
+I guess that @sc{gnu} @command{tar} up to 1.11.8 will process it as if it were an
old V7 archive, and be fooled by some fields which are coded differently.
-So, the question is to decide if the next generation of GNU @code{tar}
-should produce POSIX format by default, whenever possible, producing
-archives older versions of GNU @code{tar} might not be able to read
+So, the question is to decide if the next generation of @sc{gnu} @command{tar}
+should produce @sc{posix} format by default, whenever possible, producing
+archives older versions of @sc{gnu} @command{tar} might not be able to read
correctly. I fear that we will have to suffer such a choice one of these
-days, if we want GNU @code{tar} to go closer to POSIX. We can rush it.
-Another possibility is to produce the current GNU @code{tar} format
-by default for a few years, but have GNU @code{tar} versions from some
+days, if we want @sc{gnu} @command{tar} to go closer to @sc{posix}. We can rush it.
+Another possibility is to produce the current @sc{gnu} @command{tar} format
+by default for a few years, but have @sc{gnu} @command{tar} versions from some
1.@var{POSIX} and up able to recognize all three formats, and let older
-GNU @code{tar} fade out slowly. Then, we could switch to producing POSIX
+@sc{gnu} @command{tar} fade out slowly. Then, we could switch to producing @sc{posix}
format by default, with not much harm to those still having (very old at
-that time) GNU @code{tar} versions prior to 1.@var{POSIX}.
+that time) @sc{gnu} @command{tar} versions prior to 1.@var{POSIX}.
-POSIX format cannot represent very long names, volume headers,
+@sc{posix} format cannot represent very long names, volume headers,
splitting of files in multi-volumes, sparse files, and incremental
dumps; these would be all disallowed if @value{op-posix} or
-@code{POSIXLY_CORRECT}. Otherwise, if @code{tar} is given long
-names, or @samp{-[VMSgG]}, then it should automatically go non-POSIX.
+@env{POSIXLY_CORRECT}. Otherwise, if @command{tar} is given long
+names, or @samp{-[VMSgG]}, then it should automatically go non-@sc{posix}.
I think this is easily granted without much discussion.
-Another point is that only @code{mtime} is stored in POSIX
-archives, while GNU @code{tar} currently also store @code{atime}
-and @code{ctime}. If we want GNU @code{tar} to go closer to POSIX,
+Another point is that only @code{mtime} is stored in @sc{posix}
+archives, while @sc{gnu} @command{tar} currently also store @code{atime}
+and @code{ctime}. If we want @sc{gnu} @command{tar} to go closer to @sc{posix},
my choice would be to drop @code{atime} and @code{ctime} support on
average. On the other hand, I perceive that full dumps or incremental
dumps need @code{atime} and @code{ctime} support, so for those special
-applications, POSIX has to be avoided altogether.
+applications, @sc{posix} has to be avoided altogether.
A few users requested that @value{op-sparse} be always active by
default, I think that before replying to them, we have to decide
-if we want GNU @code{tar} to go closer to POSIX on average, while
-producing files. My choice would be to go closer to POSIX in the
+if we want @sc{gnu} @command{tar} to go closer to @sc{posix} on average, while
+producing files. My choice would be to go closer to @sc{posix} in the
long run. Besides possible double reading, I do not see any point
of not trying to save files as sparse when creating archives which
-are neither POSIX nor old-V7, so the actual @value{op-sparse} would
+are neither @sc{posix} nor old-V7, so the actual @value{op-sparse} would
become selected by default when producing such archives, whatever
the reason is. So, @value{op-sparse} alone might be redefined to force
-GNU-format archives, and recover its previous meaning from this fact.
+@sc{gnu}-format archives, and recover its previous meaning from this fact.
-GNU-format as it exists now can easily fool other POSIX @code{tar},
-as it uses fields which POSIX considers to be part of the file name
+@sc{gnu}-format as it exists now can easily fool other @sc{posix} @command{tar},
+as it uses fields which @sc{posix} considers to be part of the file name
prefix. I wonder if it would not be a good idea, in the long run,
-to try changing GNU-format so any added field (like @code{ctime},
+to try changing @sc{gnu}-format so any added field (like @code{ctime},
@code{atime}, file offset in subsequent volumes, or sparse file
descriptions) be wholly and always pushed into an extension block,
-instead of using space in the POSIX header block. I could manage
-to do that portably between future GNU @code{tar}s. So other POSIX
-@code{tar}s might be at least able to provide kind of correct listings
-for the archives produced by GNU @code{tar}, if not able to process
+instead of using space in the @sc{posix} header block. I could manage
+to do that portably between future @sc{gnu} @command{tar}s. So other @sc{posix}
+@command{tar}s might be at least able to provide kind of correct listings
+for the archives produced by @sc{gnu} @command{tar}, if not able to process
them otherwise.
-Using these projected extensions might induce older @code{tar}s to fail.
-We would use the same approach as for POSIX. I'll put out a @code{tar}
-capable of reading POSIXier, yet extended archives, but will not produce
-this format by default, in GNU mode. In a few years, when newer GNU
-@code{tar}s will have flooded out @code{tar} 1.11.X and previous, we
-could switch to producing POSIXier extended archives, with no real harm
-to users, as almost all existing GNU @code{tar}s will be ready to read
-POSIXier format. In fact, I'll do both changes at the same time, in a
-few years, and just prepare @code{tar} for both changes, without effecting
-them, from 1.@var{POSIX}. (Both changes: 1---using POSIX convention for
-getting over 100 characters; 2---avoiding mangling POSIX headers for GNU
-extensions, using only POSIX mandated extension techniques).
-
-So, a future @code{tar} will have a @value{op-posix}
-flag forcing the usage of truly POSIX headers, and so, producing
-archives previous GNU @code{tar} will not be able to read.
+Using these projected extensions might induce older @command{tar}s to fail.
+We would use the same approach as for @sc{posix}. I'll put out a @command{tar}
+capable of reading @sc{posix}ier, yet extended archives, but will not produce
+this format by default, in @sc{gnu} mode. In a few years, when newer @sc{gnu}
+@command{tar}s will have flooded out @command{tar} 1.11.X and previous, we
+could switch to producing @sc{posix}ier extended archives, with no real harm
+to users, as almost all existing @sc{gnu} @command{tar}s will be ready to read
+@sc{posix}ier format. In fact, I'll do both changes at the same time, in a
+few years, and just prepare @command{tar} for both changes, without effecting
+them, from 1.@var{POSIX}. (Both changes: 1---using @sc{posix} convention for
+getting over 100 characters; 2---avoiding mangling @sc{posix} headers for @sc{gnu}
+extensions, using only @sc{posix} mandated extension techniques).
+
+So, a future @command{tar} will have a @value{op-posix}
+flag forcing the usage of truly @sc{posix} headers, and so, producing
+archives previous @sc{gnu} @command{tar} will not be able to read.
So, @emph{once} pretest will announce that feature, it would be
particularly useful that users test how exchangeable will be archives
-between GNU @code{tar} with @value{op-posix} and other POSIX @code{tar}.
+between @sc{gnu} @command{tar} with @value{op-posix} and other @sc{posix} @command{tar}.
-In a few years, when GNU @code{tar} will produce POSIX headers by
+In a few years, when @sc{gnu} @command{tar} will produce @sc{posix} headers by
default, @value{op-posix} will have a strong meaning and will disallow
-GNU extensions. But in the meantime, for a long while, @value{op-posix}
-in GNU tar will not disallow GNU extensions like @value{op-label},
+@sc{gnu} extensions. But in the meantime, for a long while, @value{op-posix}
+in @sc{gnu} tar will not disallow @sc{gnu} extensions like @value{op-label},
@value{op-multi-volume}, @value{op-sparse}, or very long file or link names.
-However, @value{op-posix} with GNU extensions will use POSIX
+However, @value{op-posix} with @sc{gnu} extensions will use @sc{posix}
headers with reserved-for-users extensions to headers, and I will be
-curious to know how well or bad POSIX @code{tar}s will react to these.
+curious to know how well or bad @sc{posix} @command{tar}s will react to these.
-GNU @code{tar} prior to 1.@var{POSIX}, and after 1.@var{POSIX} without
+@sc{gnu} @command{tar} prior to 1.@var{POSIX}, and after 1.@var{POSIX} without
@value{op-posix}, generates and checks @samp{ustar@w{ }@w{ }}, with two
-suffixed spaces. This is sufficient for older GNU @code{tar} not to
-recognize POSIX archives, and consequently, wrongly decide those archives
-are in old V7 format. It is a useful bug for me, because GNU @code{tar}
-has other POSIX incompatibilities, and I need to segregate GNU @code{tar}
-semi-POSIX archives from truly POSIX archives, for GNU @code{tar} should
+suffixed spaces. This is sufficient for older @sc{gnu} @command{tar} not to
+recognize @sc{posix} archives, and consequently, wrongly decide those archives
+are in old V7 format. It is a useful bug for me, because @sc{gnu} @command{tar}
+has other @sc{posix} incompatibilities, and I need to segregate @sc{gnu} @command{tar}
+semi-@sc{posix} archives from truly @sc{posix} archives, for @sc{gnu} @command{tar} should
be somewhat compatible with itself, while migrating closer to latest
-POSIX standards. So, I'll be very careful about how and when I will do
+@sc{posix} standards. So, I'll be very careful about how and when I will do
the correction.
-@node Checksumming, , posix, Portability
+@node Checksumming
@subsection Checksumming Problems
-SunOS and HP-UX @code{tar} fail to accept archives created using GNU
-@code{tar} and containing non-ASCII file names, that is, file names
+SunOS and HP-UX @command{tar} fail to accept archives created using @sc{gnu}
+@command{tar} and containing non-ASCII file names, that is, file names
having characters with the eight bit set, because they use signed
-checksums, while GNU @code{tar} uses unsigned checksums while creating
-archives, as per POSIX standards. On reading, GNU @code{tar} computes
+checksums, while @sc{gnu} @command{tar} uses unsigned checksums while creating
+archives, as per @sc{posix} standards. On reading, @sc{gnu} @command{tar} computes
both checksums and accept any. It is somewhat worrying that a lot of
people may go around doing backup of their files using faulty (or at
least non-standard) software, not learning about it until it's time
to restore their missing files with an incompatible file extractor,
or vice versa.
-GNU @code{tar} compute checksums both ways, and accept any on read,
-so GNU tar can read Sun tapes even with their wrong checksums.
-GNU @code{tar} produces the standard checksum, however, raising
-incompatibilities with Sun. That is to say, GNU @code{tar} has not
+@sc{gnu} @command{tar} compute checksums both ways, and accept any on read,
+so @sc{gnu} tar can read Sun tapes even with their wrong checksums.
+@sc{gnu} @command{tar} produces the standard checksum, however, raising
+incompatibilities with Sun. That is to say, @sc{gnu} @command{tar} has not
been modified to @emph{produce} incorrect archives to be read by buggy
-@code{tar}'s. I've been told that more recent Sun @code{tar} now
+@command{tar}'s. I've been told that more recent Sun @command{tar} now
read standard archives, so maybe Sun did a similar patch, after all?
-The story seems to be that when Sun first imported @code{tar}
+The story seems to be that when Sun first imported @command{tar}
sources on their system, they recompiled it without realizing that
the checksums were computed differently, because of a change in
the default signing of @code{char}'s in their compiler. So they
started computing checksums wrongly. When they later realized their
mistake, they merely decided to stay compatible with it, and with
themselves afterwards. Presumably, but I do not really know, HP-UX
-has chosen that their @code{tar} archives to be compatible with Sun's.
-The current standards do not favor Sun @code{tar} format. In any
+has chosen that their @command{tar} archives to be compatible with Sun's.
+The current standards do not favor Sun @command{tar} format. In any
case, it now falls on the shoulders of SunOS and HP-UX users to get
-a @code{tar} able to read the good archives they receive.
-
-@node Compression, Attributes, Portability, Formats
+a @command{tar} able to read the good archives they receive.
+
+@node Large or Negative Values
+@subsection Large or Negative Values
+@cindex large values
+@cindex future time stamps
+@cindex negative time stamps
+
+@sc{posix} @command{tar} format uses fixed-sized unsigned octal strings
+to represent numeric values. User and group IDs and device major and
+minor numbers have unsigned 21-bit representations, and file sizes and
+times have unsigned 33-bit representations. @sc{gnu} @command{tar}
+generates @sc{posix} representations when possible, but for values
+outside the @sc{posix} range it generates two's-complement base-256
+strings: uids, gids, and device numbers have signed 57-bit
+representations, and file sizes and times have signed 89-bit
+representations. These representations are an extension to @sc{posix}
+@command{tar} format, so they are not universally portable.
+
+The most common portability problems with out-of-range numeric values
+are large files and future or negative time stamps.
+
+Portable archives should avoid members of 8 GB or larger, as @sc{posix}
+@command{tar} format cannot represent them.
+
+Portable archives should avoid time stamps from the future. @sc{posix}
+@command{tar} format can represent time stamps in the range 1970-01-01
+00:00:00 through 2242-03-16 12:56:31 @sc{utc}. However, many current
+hosts use a signed 32-bit @code{time_t}, or internal time stamp format,
+and cannot represent time stamps after 2038-01-19 03:14:07 @sc{utc}; so
+portable archives must avoid these time stamps for many years to come.
+
+Portable archives should also avoid time stamps before 1970. These time
+stamps are a common @sc{posix} extension but their @code{time_t}
+representations are negative. Many traditional @command{tar}
+implementations generate a two's complement representation for negative
+time stamps that assumes a signed 32-bit @code{time_t}; hence they
+generate archives that are not portable to hosts with differing
+@code{time_t} representations. @sc{gnu} @command{tar} recognizes this
+situation when it is run on host with a signed 32-bit @code{time_t}, but
+it issues a warning, as these time stamps are nonstandard and unportable.
+
+@node Compression
@section Using Less Space through Compression
@menu
* sparse:: Archiving Sparse Files
@end menu
-@node gzip, sparse, Compression, Compression
+@node gzip
@subsection Creating and Reading Compressed Archives
@cindex Compressed archives
@cindex Storing archives in compressed format
@item -z
@itemx --gzip
@itemx --ungzip
-Filter the archive through @code{gzip}.
+Filter the archive through @command{gzip}.
@end table
@FIXME{ach; these two bits orig from "compare" (?). where to put?} Some
You can use @samp{--gzip} and @samp{--gunzip} on physical devices
(tape drives, etc.) and remote files as well as on normal files; data
to or from such devices or remote files is reblocked by another copy
-of the @code{tar} program to enforce the specified (or default) record
+of the @command{tar} program to enforce the specified (or default) record
size. The default compression parameters are used; if you need to
-override them, avoid the @value{op-gzip} option and run @code{gzip}
-explicitly. (Or set the @samp{GZIP} environment variable.)
+override them, avoid the @value{op-gzip} option and run @command{gzip}
+explicitly. (Or set the @env{GZIP} environment variable.)
The @value{op-gzip} option does not work with the @value{op-multi-volume}
option, or with the @value{op-update}, @value{op-append},
@value{op-concatenate}, or @value{op-delete} operations.
-It is not exact to say that GNU @code{tar} is to work in concert
-with @code{gzip} in a way similar to @code{zip}, say. Surely, it is
-possible that @code{tar} and @code{gzip} be done with a single call,
+It is not exact to say that @sc{gnu} @command{tar} is to work in concert
+with @command{gzip} in a way similar to @command{zip}, say. Surely, it is
+possible that @command{tar} and @command{gzip} be done with a single call,
like in:
@example
to explode and unpack.
The difference is that the whole archive is compressed. With
-@code{zip}, archive members are archived individually. @code{tar}'s
+@command{zip}, archive members are archived individually. @command{tar}'s
method yields better compression. On the other hand, one can view the
-contents of a @code{zip} archive without having to decompress it. As
-for the @code{tar} and @code{gzip} tandem, you need to decompress the
+contents of a @command{zip} archive without having to decompress it. As
+for the @command{tar} and @command{gzip} tandem, you need to decompress the
archive to see its contents. However, this may be done without needing
disk space, by using pipes internally:
@end example
@cindex corrupted archives
-About corrupted compressed archives: @code{gzip}'ed files have no
+About corrupted compressed archives: @command{gzip}'ed files have no
redundancy, for maximum compression. The adaptive nature of the
compression scheme means that the compression tables are implicitly
spread all over the archive. If you lose a few blocks, the dynamic
is little chance that you could recover later in the archive.
There are pending suggestions for having a per-volume or per-file
-compression in GNU @code{tar}. This would allow for viewing the
+compression in @sc{gnu} @command{tar}. This would allow for viewing the
contents without decompression, and for resynchronizing decompression at
every volume or file, in case of corrupted archives. Doing so, we might
lose some compressibility. But this would have make recovering easier.
@item -Z
@itemx --compress
@itemx --uncompress
-Filter the archive through @code{compress}. Otherwise like @value{op-gzip}.
+Filter the archive through @command{compress}. Otherwise like @value{op-gzip}.
@item --use-compress-program=@var{prog}
Filter through @var{prog} (must accept @samp{-d}).
@value{op-compress} stores an archive in compressed format. This
option is useful in saving time over networks and space in pipes, and
when storage space is at a premium. @value{op-compress} causes
-@code{tar} to compress when writing the archive, or to uncompress when
+@command{tar} to compress when writing the archive, or to uncompress when
reading the archive.
-To perform compression and uncompression on the archive, @code{tar}
-runs the @code{compress} utility. @code{tar} uses the default
+To perform compression and uncompression on the archive, @command{tar}
+runs the @command{compress} utility. @command{tar} uses the default
compression parameters; if you need to override them, avoid the
-@value{op-compress} option and run the @code{compress} utility
-explicitly. It is useful to be able to call the @code{compress}
-utility from within @code{tar} because the @code{compress} utility by
+@value{op-compress} option and run the @command{compress} utility
+explicitly. It is useful to be able to call the @command{compress}
+utility from within @command{tar} because the @command{compress} utility by
itself cannot access remote tape drives.
The @value{op-compress} option will not work in conjunction with the
@value{op-append} and @value{op-delete} operations. @xref{Operations}, for
more information on these operations.
-If there is no compress utility available, @code{tar} will report an error.
-@strong{Please note} that the @code{compress} program may be covered by
+If there is no compress utility available, @command{tar} will report an error.
+@strong{Please note} that the @command{compress} program may be covered by
a patent, and therefore we recommend you stop using it.
@value{op-bzip2} acts like @value{op-compress}, except that it uses
@itemx --uncompress
@itemx -z
@itemx -Z
-When this option is specified, @code{tar} will compress (when writing
+When this option is specified, @command{tar} will compress (when writing
an archive), or uncompress (when reading an archive). Used in
conjunction with the @value{op-create}, @value{op-extract}, @value{op-list} and
@value{op-compare} operations.
@end table
You can have archives be compressed by using the @value{op-gzip} option.
-This will arrange for @code{tar} to use the @code{gzip} program to be
+This will arrange for @command{tar} to use the @command{gzip} program to be
used to compress or uncompress the archive wren writing or reading it.
-To use the older, obsolete, @code{compress} program, use the
-@value{op-compress} option. The GNU Project recommends you not use
-@code{compress}, because there is a patent covering the algorithm it
+To use the older, obsolete, @command{compress} program, use the
+@value{op-compress} option. The @sc{gnu} Project recommends you not use
+@command{compress}, because there is a patent covering the algorithm it
uses. You could be sued for patent infringement merely by running
-@code{compress}.
+@command{compress}.
I have one question, or maybe it's a suggestion if there isn't a way
to do it now. I would like to use @value{op-gzip}, but I'd also like the
-output to be fed through a program like GNU @code{ecc} (actually, right
+output to be fed through a program like @sc{gnu} @command{ecc} (actually, right
now that's @samp{exactly} what I'd like to use :-)), basically adding
ECC protection on top of compression. It seems as if this should be
quite easy to do, but I can't work out exactly how to go about it.
-Of course, I can pipe the standard output of @code{tar} through
-@code{ecc}, but then I lose (though I haven't started using it yet,
-I confess) the ability to have @code{tar} use @code{rmt} for it's I/O
+Of course, I can pipe the standard output of @command{tar} through
+@command{ecc}, but then I lose (though I haven't started using it yet,
+I confess) the ability to have @command{tar} use @command{rmt} for it's I/O
(I think).
I think the most straightforward thing would be to let me specify a
with the options they require specifiable), but beggars shouldn't be
choosers and anything you decide on would be fine with me.
-By the way, I like @code{ecc} but if (as the comments say) it can't
+By the way, I like @command{ecc} but if (as the comments say) it can't
deal with loss of block sync, I'm tempted to throw some time at adding
that capability. Supposing I were to actually do such a thing and
get it (apparently) working, do you accept contributed changes to
the DLT compression mode, the data will actually get bigger and one will
end up with less space on the tape.
-@node sparse, , gzip, Compression
+@node sparse
@subsection Archiving Sparse Files
@cindex Sparse Files
@UNREVISED
In later versions, this option may be removed, and the testing and
treatment of sparse files may be done automatically with any special
-GNU options. For now, it is an option needing to be specified on
+@sc{gnu} options. For now, it is an option needing to be specified on
the command line with the creation or updating of an archive.
Files in the filesystem occasionally have ``holes.'' A hole in a file
is a section of the file's contents which was never written. The
contents of a hole read as all zeros. On many operating systems,
actual disk storage is not allocated for holes, but they are counted
-in the length of the file. If you archive such a file, @code{tar}
-could create an archive longer than the original. To have @code{tar}
+in the length of the file. If you archive such a file, @command{tar}
+could create an archive longer than the original. To have @command{tar}
attempt to recognize the holes in a file, use @value{op-sparse}. When
you use the @value{op-sparse} option, then, for any file using less
-disk space than would be expected from its length, @code{tar} searches
+disk space than would be expected from its length, @command{tar} searches
the file for consecutive stretches of zeros. It then records in the
archive for the file where the consecutive stretches of zeros are, and
only archives the ``real contents'' of the file. On extraction (using
@value{op-sparse} is not needed on extraction) any such files have
hols created wherever the continuous stretches of zeros were found.
-Thus, if you use @value{op-sparse}, @code{tar} archives won't take
+Thus, if you use @value{op-sparse}, @command{tar} archives won't take
more space than the original.
A file is sparse if it contains blocks of zeros whose existence is
recorded, but that have no space allocated on disk. When you specify
the @value{op-sparse} option in conjunction with the @value{op-create}
-operation, @code{tar} tests all files for sparseness while archiving.
-If @code{tar} finds a file to be sparse, it uses a sparse representation of
+operation, @command{tar} tests all files for sparseness while archiving.
+If @command{tar} finds a file to be sparse, it uses a sparse representation of
the file in the archive. @value{xref-create}, for more information
about creating archives.
hundreds of tapes). @FIXME-xref{incremental when node name is set.}
@end quotation
-@code{tar} ignores the @value{op-sparse} option when reading an archive.
+@command{tar} ignores the @value{op-sparse} option when reading an archive.
@table @kbd
@item --sparse
the archive. Use in conjunction with write operations.
@end table
-However, users should be well aware that at archive creation time, GNU
-@code{tar} still has to read whole disk file to locate the @dfn{holes}, and
+However, users should be well aware that at archive creation time, @sc{gnu}
+@command{tar} still has to read whole disk file to locate the @dfn{holes}, and
so, even if sparse files use little space on disk and in the archive, they
may sometimes require inordinate amount of time for reading and examining
all-zero blocks of a file. Although it works, it's painfully slow for a
the @value{op-sparse} option is used or not, so by merely @emph{not}
using the option, you are not saving time@footnote{Well! We should say
the whole truth, here. When @value{op-sparse} is selected while creating
-an archive, the current @code{tar} algorithm requires sparse files to be
+an archive, the current @command{tar} algorithm requires sparse files to be
read twice, not once. We hope to develop a new archive format for saving
sparse files in which one pass will be sufficient.}.
-Programs like @code{dump} do not have to read the entire file; by examining
+Programs like @command{dump} do not have to read the entire file; by examining
the file system directly, they can determine in advance exactly where the
holes are and thus avoid reading through them. The only data it need read
-are the actual allocated data blocks. GNU @code{tar} uses a more portable
+are the actual allocated data blocks. @sc{gnu} @command{tar} uses a more portable
and straightforward archiving approach, it would be fairly difficult that
it does otherwise. Elizabeth Zwicky writes to @file{comp.unix.internals},
on 1990-12-10:
get it right.
@end quotation
-@node Attributes, Standard, Compression, Formats
+@node Attributes
@section Handling File Attributes
@UNREVISED
-When @code{tar} reads files, this causes them to have the access times
-updated. To have @code{tar} attempt to set the access times back to
+When @command{tar} reads files, this causes them to have the access times
+updated. To have @command{tar} attempt to set the access times back to
what they were before they were read, use the @value{op-atime-preserve}
option. This doesn't work for files that you don't own, unless
you're root, and it doesn't interact with incremental dumps nicely
@itemx --touch
Do not extract file modified time.
-When this option is used, @code{tar} leaves the modification times
+When this option is used, @command{tar} leaves the modification times
of the files it extracts as the time when the files were extracted,
instead of setting it to the time recorded in the archive.
archive.
This is the default behavior for the superuser,
-so this option is meaningful only for non-root users, when @code{tar}
+so this option is meaningful only for non-root users, when @command{tar}
is executed on those systems able to give files away. This is
considered as a security flaw by many people, at least because it
makes quite difficult to correctly account users for the disk space
they occupy. Also, the @code{suid} or @code{sgid} attributes of
files are easily and silently lost when files are given away.
-When writing an archive, @code{tar} writes the user id and user name
+When writing an archive, @command{tar} writes the user id and user name
separately. If it can't find a user name (because the user id is not
in @file{/etc/passwd}), then it does not write one. When restoring,
and doing a @code{chmod} like when you use @value{op-same-permissions},
had booted from an emergency floppy with no password file or put your
disk into another machine to do the restore.
-The numeric ids are @emph{always} saved into @code{tar} archives.
+The numeric ids are @emph{always} saved into @command{tar} archives.
The identifying names are added at create time when provided by the
system, unless @value{op-old-archive} is used. Numeric ids could be
used when moving archives between a collection of machines using
a centralized management for attribution of numeric ids to users
and groups. This is often made through using the NIS capabilities.
-When making a @code{tar} file for distribution to other sites, it
+When making a @command{tar} file for distribution to other sites, it
is sometimes cleaner to use a single owner for all files in the
distribution, and nicer to specify the write permission bits of the
files as stored in the archive independently of their actual value on
to have some Makefile rule creating a directory, copying all needed
files in that directory, then setting ownership and permissions as
wanted (there are a lot of possible schemes), and only then making a
-@code{tar} archive out of this directory, before cleaning everything
-out. Of course, we could add a lot of options to GNU @code{tar} for
+@command{tar} archive out of this directory, before cleaning everything
+out. Of course, we could add a lot of options to @sc{gnu} @command{tar} for
fine tuning permissions and ownership. This is not the good way,
-I think. GNU @code{tar} is already crowded with options and moreover,
+I think. @sc{gnu} @command{tar} is already crowded with options and moreover,
the approach just explained gives you a great deal of control already.
@item -p
@itemx --preserve-permissions
Extract all protection information.
-This option causes @code{tar} to set the modes (access permissions) of
+This option causes @command{tar} to set the modes (access permissions) of
extracted files exactly as recorded in the archive. If this option
is not used, the current @code{umask} setting limits the permissions
on extracted files.
@end table
-@node Standard, Extensions, Attributes, Formats
+@node Standard
@section The Standard Format
@UNREVISED
written to a storage device such as a tape or disk, sent through a
pipe or over a network, saved on the active file system, or even
stored in another archive. An archive file is not easy to read or
-manipulate without using the @code{tar} utility or Tar mode in GNU
+manipulate without using the @command{tar} utility or Tar mode in @sc{gnu}
Emacs.
Physically, an archive consists of a series of file entries terminated
entry usually describes one of the files in the archive (an
@dfn{archive member}), and consists of a file header and the contents
of the file. File headers contain file names and statistics, checksum
-information which @code{tar} uses to detect file corruption, and
+information which @command{tar} uses to detect file corruption, and
information about file types.
Archives are permitted to have more than one member with the same
same name, see -backup node, when it's written.}
In addition to entries describing archive members, an archive may
-contain entries which @code{tar} itself uses to store information.
+contain entries which @command{tar} itself uses to store information.
@value{xref-label}, for an example of such an archive entry.
-A @code{tar} archive file contains a series of blocks. Each block
+A @command{tar} archive file contains a series of blocks. Each block
contains @code{BLOCKSIZE} bytes. Although this format may be thought
of as being on magnetic tape, other media are often used.
The blocks may be @dfn{blocked} for physical I/O operations.
Each record of @var{n} blocks (where @var{n} is set by the
-@value{op-blocking-factor} option to @code{tar}) is written with a single
+@value{op-blocking-factor} option to @command{tar}) is written with a single
@w{@samp{write ()}} operation. On magnetic tapes, the result of
such a write is a single record. When writing an archive,
the last record of blocks should be written at the full size, with
whose last record is shorter than the rest, or which contains garbage
records after a zero block.
-The header block is defined in C as follows. In the GNU @code{tar}
+The header block is defined in C as follows. In the @sc{gnu} @command{tar}
distribution, this is part of file @file{src/tar.h}:
@example
Bytes representing the contents of files (after the header block
of each file) are not translated in any way and are not constrained
-to represent characters in any character set. The @code{tar} format
+to represent characters in any character set. The @command{tar} format
does not distinguish text files from binary files, and no translation
of file contents is performed.
The @code{typeflag} field specifies the type of file archived. If a
particular implementation does not recognize or permit the specified
type, the file will be extracted as if it were a regular file. As this
-action occurs, @code{tar} issues a warning to the standard error.
+action occurs, @command{tar} issues a warning to the standard error.
The @code{atime} and @code{ctime} fields are used in making incremental
backups; they store, respectively, the particular file's access time
is sparse is to look at the number blocks allocated for it versus the
number of characters in the file; if there are fewer blocks allocated
for the file than would normally be allocated for a file of that
-size, then the file is sparse. This is the method @code{tar} uses to
+size, then the file is sparse. This is the method @command{tar} uses to
detect a sparse file, and once such a file is detected, it is treated
differently from non-sparse files.
the file. Such files can appear to be very large when an @samp{ls
-l} is done on them, when in truth, there may be a very small amount
of important data contained in the file. It is thus undesirable
-to have @code{tar} think that it must back up this entire file, as
+to have @command{tar} think that it must back up this entire file, as
great quantities of room are wasted on empty blocks, which can lead
to running out of room on a tape far earlier than is necessary.
Thus, sparse files are dealt with so that these empty blocks are
@item @code{REGTYPE}
@itemx @code{AREGTYPE}
These flags represent a regular file. In order to be compatible
-with older versions of @code{tar}, a @code{typeflag} value of
+with older versions of @command{tar}, a @code{typeflag} value of
@code{AREGTYPE} should be silently recognized as a regular file.
New archives should be created using @code{REGTYPE}. Also, for
-backward compatibility, @code{tar} treats a regular file whose name
+backward compatibility, @command{tar} treats a regular file whose name
ends with a slash as a directory.
@item @code{LNKTYPE}
@item @code{A} @dots{} @code{Z}
These are reserved for custom implementations. Some of these are
-used in the GNU modified format, as described below.
+used in the @sc{gnu} modified format, as described below.
@end table
Other values are reserved for specification in future revisions of
-the P1003 standard, and should not be used by any @code{tar} program.
+the P1003 standard, and should not be used by any @command{tar} program.
The @code{magic} field indicates that this archive was output in
the P1003 archive format. If this field contains @code{TMAGIC},
IEEE Std 1003.2-1992, pages 380-388 (section 4.48) and pages 936-940
(section E.4.48) for @cite{pax - Portable archive interchange}.
-@node Extensions, cpio, Standard, Formats
-@section GNU Extensions to the Archive Format
+@node Extensions
+@section @sc{gnu} Extensions to the Archive Format
@UNREVISED
-The GNU format uses additional file types to describe new types of
+The @sc{gnu} format uses additional file types to describe new types of
files in an archive. These are listed below.
@table @code
@end table
-You may have trouble reading a GNU format archive on a non-GNU
+You may have trouble reading a @sc{gnu} format archive on a non-@sc{gnu}
system if the options @value{op-incremental}, @value{op-multi-volume},
@value{op-sparse}, or @value{op-label} were used when writing the archive.
-In general, if @code{tar} does not use the GNU-added fields of the
-header, other versions of @code{tar} should be able to read the
-archive. Otherwise, the @code{tar} program will give an error, the
+In general, if @command{tar} does not use the @sc{gnu}-added fields of the
+header, other versions of @command{tar} should be able to read the
+archive. Otherwise, the @command{tar} program will give an error, the
most likely one being a checksum error.
-@node cpio, , Extensions, Formats
-@section Comparison of @code{tar} and @code{cpio}
+@node cpio
+@section Comparison of @command{tar} and @command{cpio}
@UNREVISED
@FIXME{Reorganize the following material}
-The @code{cpio} archive formats, like @code{tar}, do have maximum
+The @command{cpio} archive formats, like @command{tar}, do have maximum
pathname lengths. The binary and old ASCII formats have a max path
length of 256, and the new ASCII and CRC ASCII formats have a max
-path length of 1024. GNU @code{cpio} can read and write archives
-with arbitrary pathname lengths, but other @code{cpio} implementations
+path length of 1024. @sc{gnu} @command{cpio} can read and write archives
+with arbitrary pathname lengths, but other @command{cpio} implementations
may crash unexplainedly trying to read them.
-@code{tar} handles symbolic links in the form in which it comes in BSD;
-@code{cpio} doesn't handle symbolic links in the form in which it comes
+@command{tar} handles symbolic links in the form in which it comes in BSD;
+@command{cpio} doesn't handle symbolic links in the form in which it comes
in System V prior to SVR4, and some vendors may have added symlinks
-to their system without enhancing @code{cpio} to know about them.
+to their system without enhancing @command{cpio} to know about them.
Others may have enhanced it in a way other than the way I did it
at Sun, and which was adopted by AT&T (and which is, I think, also
-present in the @code{cpio} that Berkeley picked up from AT&T and put
+present in the @command{cpio} that Berkeley picked up from AT&T and put
into a later BSD release---I think I gave them my changes).
-(SVR4 does some funny stuff with @code{tar}; basically, its @code{cpio}
-can handle @code{tar} format input, and write it on output, and it
+(SVR4 does some funny stuff with @command{tar}; basically, its @command{cpio}
+can handle @command{tar} format input, and write it on output, and it
probably handles symbolic links. They may not have bothered doing
-anything to enhance @code{tar} as a result.)
+anything to enhance @command{tar} as a result.)
-@code{cpio} handles special files; traditional @code{tar} doesn't.
+@command{cpio} handles special files; traditional @command{tar} doesn't.
-@code{tar} comes with V7, System III, System V, and BSD source;
-@code{cpio} comes only with System III, System V, and later BSD
+@command{tar} comes with V7, System III, System V, and BSD source;
+@command{cpio} comes only with System III, System V, and later BSD
(4.3-tahoe and later).
-@code{tar}'s way of handling multiple hard links to a file can handle
+@command{tar}'s way of handling multiple hard links to a file can handle
file systems that support 32-bit inumbers (e.g., the BSD file system);
-@code{cpio}s way requires you to play some games (in its "binary"
+@command{cpio}s way requires you to play some games (in its "binary"
format, i-numbers are only 16 bits, and in its "portable ASCII" format,
they're 18 bits---it would have to play games with the "file system ID"
field of the header to make sure that the file system ID/i-number pairs
of different files were always different), and I don't know which
-@code{cpio}s, if any, play those games. Those that don't might get
+@command{cpio}s, if any, play those games. Those that don't might get
confused and think two files are the same file when they're not, and
make hard links between them.
-@code{tar}s way of handling multiple hard links to a file places only
+@command{tar}s way of handling multiple hard links to a file places only
one copy of the link on the tape, but the name attached to that copy
-is the @emph{only} one you can use to retrieve the file; @code{cpio}s
+is the @emph{only} one you can use to retrieve the file; @command{cpio}s
way puts one copy for every link, but you can retrieve it using any
of the names.
What type of check sum (if any) is used, and how is this calculated.
@end quotation
-See the attached manual pages for @code{tar} and @code{cpio} format.
-@code{tar} uses a checksum which is the sum of all the bytes in the
-@code{tar} header for a file; @code{cpio} uses no checksum.
+See the attached manual pages for @command{tar} and @command{cpio} format.
+@command{tar} uses a checksum which is the sum of all the bytes in the
+@command{tar} header for a file; @command{cpio} uses no checksum.
@quotation
-If anyone knows why @code{cpio} was made when @code{tar} was present
+If anyone knows why @command{cpio} was made when @command{tar} was present
at the unix scene,
@end quotation
-It wasn't. @code{cpio} first showed up in PWB/UNIX 1.0; no
-generally-available version of UNIX had @code{tar} at the time. I don't
+It wasn't. @command{cpio} first showed up in PWB/UNIX 1.0; no
+generally-available version of UNIX had @command{tar} at the time. I don't
know whether any version that was generally available @emph{within AT&T}
-had @code{tar}, or, if so, whether the people within AT&T who did
-@code{cpio} knew about it.
+had @command{tar}, or, if so, whether the people within AT&T who did
+@command{cpio} knew about it.
-On restore, if there is a corruption on a tape @code{tar} will stop at
-that point, while @code{cpio} will skip over it and try to restore the
+On restore, if there is a corruption on a tape @command{tar} will stop at
+that point, while @command{cpio} will skip over it and try to restore the
rest of the files.
The main difference is just in the command syntax and header format.
-@code{tar} is a little more tape-oriented in that everything is blocked
+@command{tar} is a little more tape-oriented in that everything is blocked
to start on a record boundary.
@quotation
crashed archives at all.)
@end quotation
-Theoretically it should be easier under @code{tar} since the blocking
+Theoretically it should be easier under @command{tar} since the blocking
lets you find a header with some variation of @samp{dd skip=@var{nn}}.
-However, modern @code{cpio}'s and variations have an option to just
+However, modern @command{cpio}'s and variations have an option to just
search for the next file header after an error with a reasonable chance
of resyncing. However, lots of tape driver software won't allow you to
continue past a media error which should be the only reason for getting
archive.
@quotation
-If anyone knows why @code{cpio} was made when @code{tar} was present
+If anyone knows why @command{cpio} was made when @command{tar} was present
at the unix scene, please tell me about this too.
@end quotation
Probably because it is more media efficient (by not blocking everything
-and using only the space needed for the headers where @code{tar}
+and using only the space needed for the headers where @command{tar}
always uses 512 bytes per file header) and it knows how to archive
special files.
You might want to look at the freely available alternatives. The major
-ones are @code{afio}, GNU @code{tar}, and @code{pax}, each of which
+ones are @command{afio}, @sc{gnu} @command{tar}, and @command{pax}, each of which
have their own extensions with some backwards compatibility.
-Sparse files were @code{tar}red as sparse files (which you can easily
-test, because the resulting archive gets smaller, and GNU @code{cpio}
+Sparse files were @command{tar}red as sparse files (which you can easily
+test, because the resulting archive gets smaller, and @sc{gnu} @command{cpio}
can no longer read it).
-@node Media, Index, Formats, Top
+@node Media
@chapter Tapes and Other Archive Media
@UNREVISED
A few special cases about tape handling warrant more detailed
description. These special cases are discussed below.
-Many complexities surround the use of @code{tar} on tape drives. Since
+Many complexities surround the use of @command{tar} on tape drives. Since
the creation and manipulation of archives located on magnetic tape was
-the original purpose of @code{tar}, it contains many features making
+the original purpose of @command{tar}, it contains many features making
such manipulation easier.
Archives are usually written on dismountable media---tape cartridges,
* Write Protection::
@end menu
-@node Device, Remote Tape Server, Media, Media
+@node Device
@section Device Selection and Switching
@UNREVISED
Use archive file or device @var{file} on @var{hostname}.
@end table
-This option is used to specify the file name of the archive @code{tar}
+This option is used to specify the file name of the archive @command{tar}
works on.
-If the file name is @samp{-}, @code{tar} reads the archive from standard
+If the file name is @samp{-}, @command{tar} reads the archive from standard
input (when listing or extracting), or writes it to standard output
(when creating). If the @samp{-} file name is given when updating an
-archive, @code{tar} will read the original archive from its standard
+archive, @command{tar} will read the original archive from its standard
input, and will write the entire new archive to its standard output.
If the file name contains a @samp{:}, it is interpreted as
@samp{hostname:file name}. If the @var{hostname} contains an @dfn{at}
sign (@kbd{@@}), it is treated as @samp{user@@hostname:file name}. In
-either case, @code{tar} will invoke the command @code{rsh} (or
-@code{remsh}) to start up an @file{/etc/rmt} on the remote machine. If
-you give an alternate login name, it will be given to the @code{rsh}.
+either case, @command{tar} will invoke the command @command{rsh} (or
+@command{remsh}) to start up an @file{/etc/rmt} on the remote machine. If
+you give an alternate login name, it will be given to the @command{rsh}.
Naturally, the remote machine must have an executable @file{/etc/rmt}.
This program is free software from the University of California, and a
-copy of the source code can be found with the sources for @code{tar};
+copy of the source code can be found with the sources for @command{tar};
it's compiled and installed by default.
-If this option is not given, but the environment variable @code{TAPE} is
-set, its value is used; otherwise, old versions of @code{tar} used a default
-archive name (which was picked when @code{tar} was compiled). The
+If this option is not given, but the environment variable @env{TAPE} is
+set, its value is used; otherwise, old versions of @command{tar} used a default
+archive name (which was picked when @command{tar} was compiled). The
default is normally set up to be the @dfn{first} tape drive or other
transportable I/O medium on the system.
-Starting with version 1.11.5, GNU @code{tar} uses standard input and
+Starting with version 1.11.5, @sc{gnu} @command{tar} uses standard input and
standard output as the default device, and I will not try anymore
supporting automatic device detection at installation time. This was
failing really in too many cases, it was hopeless. This is now
completely left to the installer to override standard input and standard
output for default device, if this seems preferable.
-Further, I think @emph{most} actual usages of @code{tar} are done with
+Further, I think @emph{most} actual usages of @command{tar} are done with
pipes or disks, not really tapes, cartridges or diskettes.
Some users think that using standard input and output is running
all this mess, using standard input and output as a default really
sounds like the only clean choice left, and a very useful one too.
-GNU @code{tar} reads and writes archive in records, I suspect this is the
+@sc{gnu} @command{tar} reads and writes archive in records, I suspect this is the
main reason why block devices are preferred over character devices.
Most probably, block devices are more efficient too. The installer
could also check for @samp{DEFTAPE} in @file{<sys/mtio.h>}.
Archive file is local even if it contains a colon.
@item --rsh-command=@var{command}
-Use remote @var{command} instead of @code{rsh}. This option exists
-so that people who use something other than the standard @code{rsh}
-(e.g., a Kerberized @code{rsh}) can access a remote device.
+Use remote @var{command} instead of @command{rsh}. This option exists
+so that people who use something other than the standard @command{rsh}
+(e.g., a Kerberized @command{rsh}) can access a remote device.
When this command is not used, the shell command found when
-the @code{tar} program was installed is used instead. This is
+the @command{tar} program was installed is used instead. This is
the first found of @file{/usr/ucb/rsh}, @file{/usr/bin/remsh},
@file{/usr/bin/rsh}, @file{/usr/bsd/rsh} or @file{/usr/bin/nsh}.
The installer may have overridden this by defining the environment
-variable @code{RSH} @emph{at installation time}.
+variable @env{RSH} @emph{at installation time}.
@item -[0-7][lmh]
Specify drive and density.
@itemx --multi-volume
Create/list/extract multi-volume archive.
-This option causes @code{tar} to write a @dfn{multi-volume} archive---one
+This option causes @command{tar} to write a @dfn{multi-volume} archive---one
that may be larger than will fit on the medium used to hold it.
@xref{Multi-Volume Archives}.
@value{op-multi-volume}.
@end table
-@node Remote Tape Server, Common Problems and Solutions, Device, Media
+@node Remote Tape Server
@section The Remote Tape Server
@cindex remote tape drive
@pindex rmt
-In order to access the tape drive on a remote machine, @code{tar}
+In order to access the tape drive on a remote machine, @command{tar}
uses the remote tape server written at the University of California at
Berkeley. The remote tape server must be installed as @file{/etc/rmt}
-on any machine whose tape drive you want to use. @code{tar} calls
-@file{/etc/rmt} by running an @code{rsh} or @code{remsh} to the remote
+on any machine whose tape drive you want to use. @command{tar} calls
+@file{/etc/rmt} by running an @command{rsh} or @command{remsh} to the remote
machine, optionally using a different login name if one is supplied.
A copy of the source for the remote tape server is provided. It is
and installing it are included in the @file{Makefile}.
@cindex absolute file names
-Unless you use the @value{op-absolute-names} option, GNU @code{tar} will
+Unless you use the @value{op-absolute-names} option, @sc{gnu} @command{tar} will
not allow you to create an archive that contains absolute file names
-(a file name beginning with @samp{/}.) If you try, @code{tar} will
+(a file name beginning with @samp{/}.) If you try, @command{tar} will
automatically remove the leading @samp{/} from the file names it
stores in the archive. It will also type a warning message telling
you what it is doing.
-When reading an archive that was created with a different @code{tar}
-program, GNU @code{tar} automatically extracts entries in the archive
+When reading an archive that was created with a different @command{tar}
+program, @sc{gnu} @command{tar} automatically extracts entries in the archive
which have absolute file names as if the file names were not absolute.
This is an important feature. A visitor here once gave a
-@code{tar} tape to an operator to restore; the operator used Sun @code{tar}
-instead of GNU @code{tar}, and the result was that it replaced large
+@command{tar} tape to an operator to restore; the operator used Sun @command{tar}
+instead of @sc{gnu} @command{tar}, and the result was that it replaced large
portions of our @file{/bin} and friends with versions from the tape;
needless to say, we were unhappy about having to recover the file system
from backup tapes.
For example, if the archive contained a file @file{/usr/bin/computoy},
-GNU @code{tar} would extract the file to @file{usr/bin/computoy},
+@sc{gnu} @command{tar} would extract the file to @file{usr/bin/computoy},
relative to the current directory. If you want to extract the files in
an archive to the same absolute names that they had when the archive
was created, you should do a @samp{cd /} before extracting the files
working correctly. The best workaround at the moment is to use a
significantly larger blocking factor than the default 20.
-In order to update an archive, @code{tar} must be able to backspace the
+In order to update an archive, @command{tar} must be able to backspace the
archive in order to reread or rewrite a record that was just read (or
written). This is currently possible only on two kinds of files: normal
disk files (or any other file that can be backspaced with @samp{lseek}),
means these commands and options will never be able to work on them.
These non-backspacing media include pipes and cartridge tape drives.
-Some other media can be backspaced, and @code{tar} will work on them
-once @code{tar} is modified to do so.
+Some other media can be backspaced, and @command{tar} will work on them
+once @command{tar} is modified to do so.
Archives created with the @value{op-multi-volume}, @value{op-label}, and
@value{op-incremental} options may not be readable by other version
-of @code{tar}. In particular, restoring a file that was split over
-a volume boundary will require some careful work with @code{dd}, if
-it can be done at all. Other versions of @code{tar} may also create
+of @command{tar}. In particular, restoring a file that was split over
+a volume boundary will require some careful work with @command{dd}, if
+it can be done at all. Other versions of @command{tar} may also create
an empty file whose name is that of the volume header. Some versions
-of @code{tar} may create normal files instead of directories archived
+of @command{tar} may create normal files instead of directories archived
with the @value{op-incremental} option.
-@node Common Problems and Solutions, Blocking, Remote Tape Server, Media
+@node Common Problems and Solutions
@section Some Common Problems and their Solutions
@ifclear PUBLISH
no such file or directory
not owner
-errors from @code{tar}:
+errors from @command{tar}:
directory checksum error
header format error
@end ifclear
-@node Blocking, Many, Common Problems and Solutions, Media
+@node Blocking
@section Blocking
@UNREVISED
the next two paragraphs, as the remainder of this manual uses those
two terms in a quite consistent way.
-John Gilmore, the writer of the public domain @code{tar} from which
-GNU @code{tar} was originally derived, wrote (June 1995):
+John Gilmore, the writer of the public domain @command{tar} from which
+@sc{gnu} @command{tar} was originally derived, wrote (June 1995):
@quotation
The nomenclature of tape drives comes from IBM, where I believe
occupy more than one block), etc. The @code{JCL} @samp{DD RECFORM=}
parameter specified this to the operating system.
-The Unix man page on @code{tar} was totally confused about this.
+The Unix man page on @command{tar} was totally confused about this.
When I wrote @code{PD TAR}, I used the historically correct terminology
-(@code{tar} writes data records, which are grouped into blocks).
-It appears that the bogus terminology made it into POSIX (no surprise
+(@command{tar} writes data records, which are grouped into blocks).
+It appears that the bogus terminology made it into @sc{posix} (no surprise
here), and now Fran@,{c}ois has migrated that terminology back
into the source code too.
@end quotation
being lost. In this manual, the term @dfn{block} usually refers to
a disk physical block, @emph{assuming} that each disk block is 512
bytes in length. It is true that some disk devices have different
-physical blocks, but @code{tar} ignore these differences in its own
-format, which is meant to be portable, so a @code{tar} block is always
-512 bytes in length, and @dfn{block} always mean a @code{tar} block.
+physical blocks, but @command{tar} ignore these differences in its own
+format, which is meant to be portable, so a @command{tar} block is always
+512 bytes in length, and @dfn{block} always mean a @command{tar} block.
The term @dfn{logical block} often represents the basic chunk of
allocation of many disk blocks as a single entity, which the operating
system treats somewhat atomically; this concept is only barely used
-in GNU @code{tar}.
+in @sc{gnu} @command{tar}.
The term @dfn{physical record} is another way to speak of a physical
block, those two terms are somewhat interchangeable. In this manual,
the term @dfn{record} usually refers to a tape physical block,
-@emph{assuming} that the @code{tar} archive is kept on magnetic tape.
+@emph{assuming} that the @command{tar} archive is kept on magnetic tape.
It is true that archives may be put on disk or used with pipes,
-but nevertheless, @code{tar} tries to read and write the archive one
+but nevertheless, @command{tar} tries to read and write the archive one
@dfn{record} at a time, whatever the medium in use. One record is made
up of an integral number of blocks, and this operation of putting many
disk blocks into a single tape block is called @dfn{reblocking}, or
to the application. The term @dfn{unit record} describes a small set
of characters which are transmitted whole to or by the application,
and often refers to a line of text. Those two last terms are unrelated
-to what we call a @dfn{record} in GNU @code{tar}.
+to what we call a @dfn{record} in @sc{gnu} @command{tar}.
-When writing to tapes, @code{tar} writes the contents of the archive
+When writing to tapes, @command{tar} writes the contents of the archive
in chunks known as @dfn{records}. To change the default blocking
factor, use the @value{op-blocking-factor} option. Each record will
-then be composed of @var{512-size} blocks. (Each @code{tar} block is
+then be composed of @var{512-size} blocks. (Each @command{tar} block is
512 bytes. @xref{Standard}.) Each file written to the archive uses
at least one full record. As a result, using a larger record size
can result in more wasted space for small files. On the other hand, a
honor the blocking), but not as dramatically as on tape drives that
honor blocking.
-When reading an archive, @code{tar} can usually figure out the record
+When reading an archive, @command{tar} can usually figure out the record
size on itself. When this is the case, and a non-standard record size
-was used when the archive was created, @code{tar} will print a message
+was used when the archive was created, @command{tar} will print a message
about a non-standard blocking factor, and then operate normally. On
-some tape devices, however, @code{tar} cannot figure out the record size
+some tape devices, however, @command{tar} cannot figure out the record size
itself. On most of those, you can specify a blocking factor (with
@value{op-blocking-factor}) larger than the actual blocking factor, and then use
the @value{op-read-full-records} option. (If you specify a blocking factor
with @value{op-blocking-factor} and don't use the @value{op-read-full-records}
-option, then @code{tar} will not attempt to figure out the recording size
+option, then @command{tar} will not attempt to figure out the recording size
itself.) On some devices, you must always specify the record size
-exactly with @value{op-blocking-factor} when reading, because @code{tar} cannot
+exactly with @value{op-blocking-factor} when reading, because @command{tar} cannot
figure it out. In any case, use @value{op-list} before doing any
-extractions to see whether @code{tar} is reading the archive correctly.
+extractions to see whether @command{tar} is reading the archive correctly.
-@code{tar} blocks are all fixed size (512 bytes), and its scheme for
+@command{tar} blocks are all fixed size (512 bytes), and its scheme for
putting them into records is to put a whole number of them (one or
-more) into each record. @code{tar} records are all the same size;
+more) into each record. @command{tar} records are all the same size;
at the end of the file there's a block containing all zeros, which
is how you tell that the remainder of the last record(s) are garbage.
-In a standard @code{tar} file (no options), the block size is 512
+In a standard @command{tar} file (no options), the block size is 512
and the record size is 10240, for a blocking factor of 20. What the
@value{op-blocking-factor} option does is sets the blocking factor,
changing the record size while leaving the block size at 512 bytes.
to use a factor of the order of 2048, say, giving a record size of
around one megabyte.
-If you use a blocking factor larger than 20, older @code{tar} programs
+If you use a blocking factor larger than 20, older @command{tar} programs
might not be able to read the archive, so we recommend this as a limit
-to use in practice. GNU @code{tar}, however, will support arbitrarily
+to use in practice. @sc{gnu} @command{tar}, however, will support arbitrarily
large record sizes, limited only by the amount of virtual memory or the
physical characteristics of the tape device.
* Blocking Factor:: The Blocking Factor of an Archive
@end menu
-@node Format Variations, Blocking Factor, Blocking, Blocking
+@node Format Variations
@subsection Format Variations
@cindex Format Parameters
@cindex Format Options
To specify format parameters when accessing or creating an archive,
you can use the options described in the following sections.
-If you do not specify any format parameters, @code{tar} uses
+If you do not specify any format parameters, @command{tar} uses
default parameters. You cannot modify a compressed archive.
If you create an archive with the @value{op-blocking-factor} option
specified (@value{pxref-blocking-factor}), you must specify that
blocking-factor when operating on the archive. @xref{Formats}, for other
examples of format parameter considerations.
-@node Blocking Factor, , Format Variations, Blocking
+@node Blocking Factor
@subsection The Blocking Factor of an Archive
@cindex Blocking Factor
@cindex Record Size
archiving on cartridge, a very large blocking factor (say 126 or more)
greatly increases performance. A smaller blocking factor, on the other
hand, may be useful when archiving small files, to avoid archiving lots
-of nulls as @code{tar} fills out the archive to the end of the record.
+of nulls as @command{tar} fills out the archive to the end of the record.
In general, the ideal record size depends on the size of the
inter-record gaps on the tape you are using, and the average size of the
files you are archiving. @xref{create}, for information on
@FIXME{Need example of using a cartridge with blocking factor=126 or more.}
Archives with blocking factors larger than 20 cannot be read
-by very old versions of @code{tar}, or by some newer versions
-of @code{tar} running on old machines with small address spaces.
-With GNU @code{tar}, the blocking factor of an archive is limited
+by very old versions of @command{tar}, or by some newer versions
+of @command{tar} running on old machines with small address spaces.
+With @sc{gnu} @command{tar}, the blocking factor of an archive is limited
only by the maximum record size of the device containing the archive,
or by the amount of available virtual memory.
@end example
@noindent
-In such cases, it sometimes happen that the @code{tar} bundled by the
-system is aware of block size idiosyncrasies, while GNU @code{tar} requires
+In such cases, it sometimes happen that the @command{tar} bundled by the
+system is aware of block size idiosyncrasies, while @sc{gnu} @command{tar} requires
an explicit specification for the block size, which it cannot guess.
-This yields some people to consider GNU @code{tar} is misbehaving, because
-by comparison, @cite{the bundle @code{tar} works OK}. Adding @w{@kbd{-b
+This yields some people to consider @sc{gnu} @command{tar} is misbehaving, because
+by comparison, @cite{the bundle @command{tar} works OK}. Adding @w{@kbd{-b
256}}, for example, might resolve the problem.
If you use a non-default blocking factor when you create an archive, you
must specify the same blocking factor when you modify that archive. Some
archive devices will also require you to specify the blocking factor when
reading that archive, however this is not typically the case. Usually, you
-can use @value{op-list} without specifying a blocking factor---@code{tar}
+can use @value{op-list} without specifying a blocking factor---@command{tar}
reports a non-default record size and then lists the archive members as
it would normally. To extract files from an archive with a non-standard
blocking factor (particularly if you're not sure what the blocking factor
Set record size to @math{@var{blocks} * 512} bytes.
This option is used to specify a @dfn{blocking factor} for the archive.
-When reading or writing the archive, @code{tar}, will do reads and writes
+When reading or writing the archive, @command{tar}, will do reads and writes
of the archive in records of @math{@var{block}*512} bytes. This is true
even when the archive is compressed. Some devices requires that all
-write operations be a multiple of a certain size, and so, @code{tar}
+write operations be a multiple of a certain size, and so, @command{tar}
pads the archive out to the next record boundary.
-The default blocking factor is set when @code{tar} is compiled, and is
+The default blocking factor is set when @command{tar} is compiled, and is
typically 20. Blocking factors larger than 20 cannot be read by very
-old versions of @code{tar}, or by some newer versions of @code{tar}
+old versions of @command{tar}, or by some newer versions of @command{tar}
running on old machines with small address spaces.
With a magnetic tape, larger records give faster throughput and fit
seems to dissapper. Id est, we are using block size of 112 right
now, and we haven't had the problem since we switched@dots{}
-With GNU @code{tar} the blocking factor is limited only by the maximum
+With @sc{gnu} @command{tar} the blocking factor is limited only by the maximum
record size of the device containing the archive, or by the amount of
available virtual memory.
the archive is directly handled to a local disk, instead of any special
device,
@item
-@value{op-blocking-factor} is not explicitly specified on the @code{tar}
+@value{op-blocking-factor} is not explicitly specified on the @command{tar}
invocation.
@end itemize
-In previous versions of GNU @code{tar}, the @samp{--compress-block}
+In previous versions of @sc{gnu} @command{tar}, the @samp{--compress-block}
option (or even older: @samp{--block-compress}) was necessary to
reblock compressed archives. It is now a dummy option just asking
not to be used, and otherwise ignored. If the output goes directly
@itemize @bullet
@item
-@code{gzip} will complain about trailing garbage if asked to
+@command{gzip} will complain about trailing garbage if asked to
uncompress a compressed archive on tape, there is an option to turn
the message off, but it breaks the regularity of simply having to use
@samp{@var{prog} -d} for decompression. It would be nice if gzip was
Gailly, by sending a copy of this message to him.
@item
-@code{compress} does not show this problem, but as Jean-loup pointed
+@command{compress} does not show this problem, but as Jean-loup pointed
out to Michael, @samp{compress -d} silently adds garbage after
the result of decompression, which tar ignores because it already
recognized its end-of-file indicator. So this bug may be safely
@item
@samp{gzip -d -q} will be silent about the trailing zeros indeed,
but will still return an exit status of 2 which tar reports in turn.
-@code{tar} might ignore the exit status returned, but I hate doing
-that, as it weakens the protection @code{tar} offers users against
-other possible problems at decompression time. If @code{gzip} was
+@command{tar} might ignore the exit status returned, but I hate doing
+that, as it weakens the protection @command{tar} offers users against
+other possible problems at decompression time. If @command{gzip} was
silently skipping trailing zeros @emph{and} also avoiding setting the
exit status in this innocuous case, that would solve this situation.
@item
-@code{tar} should become more solid at not stopping to read a pipe at
+@command{tar} should become more solid at not stopping to read a pipe at
the first null block encountered. This inelegantly breaks the pipe.
-@code{tar} should rather drain the pipe out before exiting itself.
+@command{tar} should rather drain the pipe out before exiting itself.
@end itemize
@item -i
@itemx --ignore-zeros
Ignore blocks of zeros in archive (means EOF).
-The @value{op-ignore-zeros} option causes @code{tar} to ignore blocks
+The @value{op-ignore-zeros} option causes @command{tar} to ignore blocks
of zeros in the archive. Normally a block of zeros indicates the
end of the archive, but when reading a damaged archive, or one which
-was created by @code{cat}-ing several archives together, this option
-allows @code{tar} to read the entire archive. This option is not on
-by default because many versions of @code{tar} write garbage after
+was created by concatenating several archives together, this option
+allows @command{tar} to read the entire archive. This option is not on
+by default because many versions of @command{tar} write garbage after
the zeroed blocks.
-Note that this option causes @code{tar} to read to the end of the
+Note that this option causes @command{tar} to read to the end of the
archive file, which may sometimes avoid problems when multiple files
are stored on a single physical tape.
@itemx --read-full-records
Reblock as we read (for reading 4.2BSD pipes).
-If @value{op-read-full-records} is used, @code{tar} will not panic if an
+If @value{op-read-full-records} is used, @command{tar} will not panic if an
attempt to read a record from the archive does not return a full record.
-Instead, @code{tar} will keep reading until it has obtained a full
+Instead, @command{tar} will keep reading until it has obtained a full
record.
-This option is turned on by default when @code{tar} is reading
+This option is turned on by default when @command{tar} is reading
an archive from standard input, or from a remote machine. This is
because on BSD Unix systems, a read of a pipe will return however
-much happens to be in the pipe, even if it is less than @code{tar}
-requested. If this option was not used, @code{tar} would fail as
+much happens to be in the pipe, even if it is less than @command{tar}
+requested. If this option was not used, @command{tar} would fail as
soon as it read an incomplete record from the pipe.
This option is also useful with the commands for updating an archive.
required to receive at once the whole record. Further, if there is a
reading error on a huge record, this is less likely that the system will
succeed in recovering the information. So, blocking should not be too
-low, nor it should be too high. @code{tar} uses by default a blocking of
+low, nor it should be too high. @command{tar} uses by default a blocking of
20 for historical reasons, and it does not really matter when reading or
writing to disk. Current tape technology would easily accommodate higher
blockings. Sun recommends a blocking of 126 for Exabytes and 96 for DATs.
@samp{--block-number}, so @samp{--block} will then expand to
@samp{--blocking-factor} unambiguously.
-@node Many, Using Multiple Tapes, Blocking, Media
+@node Many
@section Many Archives on One Tape
@FIXME{Appropriate options should be moved here from elsewhere.}
device.
A rewinding tape device will bring back the tape to its beginning point
-automatically when this device is opened or closed. Since @code{tar}
+automatically when this device is opened or closed. Since @command{tar}
opens the archive file before using it and closes it afterwards, this
means that a simple:
@cindex tape positioning
So, a rewinding device is normally meant to hold one and only one file.
-If you want to put more than one @code{tar} archive on a given tape, you
+If you want to put more than one @command{tar} archive on a given tape, you
will need to avoid using the rewinding version of the tape device. You
will also have to pay special attention to tape positioning. Errors in
positioning may overwrite the valuable data already on your tape. Many
An empty file (that is to say, two tape marks in a row) signal the
logical end of the tape, after which no file exist. Usually,
non-rewinding tape device drivers will react to the close request issued
-by @code{tar} by first writing two tape marks after your archive, and by
+by @command{tar} by first writing two tape marks after your archive, and by
backspacing over one of these. So, if you remove the tape at that time
from the tape drive, it is properly terminated. But if you write
another file at the current position, the second tape mark will be
@menu
* Tape Positioning:: Tape Positions and Tape Marks
-* mt:: The @code{mt} Utility
+* mt:: The @command{mt} Utility
@end menu
-@node Tape Positioning, mt, Many, Many
+@node Tape Positioning
@subsection Tape Positions and Tape Marks
@UNREVISED
Tape devices read and write tapes using a read/write @dfn{tape
head}---a physical part of the device which can only access one
-point on the tape at a time. When you use @code{tar} to read or
+point on the tape at a time. When you use @command{tar} to read or
write archive data from a tape device, the device will begin reading
or writing from wherever on the tape the tape head happens to be,
regardless of which archive or what part of the archive the tape
rrrr*rrrrrr*rrrrr*rr*rrrrr*rrr*rrrr**----------------
@end example
-@node mt, , Tape Positioning, Many
-@subsection The @code{mt} Utility
+@node mt
+@subsection The @command{mt} Utility
@UNREVISED
@FIXME{Is it true that this only works on non-block devices?
should explain the difference, (fixed or variable).}
@value{xref-blocking-factor}.
-You can use the @code{mt} utility to advance or rewind a tape past a
+You can use the @command{mt} utility to advance or rewind a tape past a
specified number of archive files on the tape. This will allow you
to move to the beginning of an archive before extracting or reading
it, or to the end of all the archives before writing a new one.
@FIXME{Why isn't there an "advance 'til you find two tape marks
together"?}
-The syntax of the @code{mt} command is:
+The syntax of the @command{mt} command is:
@example
@kbd{mt [-f @var{tapename}] @var{operation} [@var{number}]}
@FIXME{Is there a better way to frob the spacing on the list?}
-If you don't specify a @var{tapename}, @code{mt} uses the environment
-variable TAPE; if TAPE does not exist, @code{mt} uses the device
+If you don't specify a @var{tapename}, @command{mt} uses the environment
+variable @env{TAPE}; if @env{TAPE} is not set, @command{mt} uses the device
@file{/dev/rmt12}.
-@code{mt} returns a 0 exit status when the operation(s) were
+@command{mt} returns a 0 exit status when the operation(s) were
successful, 1 if the command was unrecognized, and 2 if an operation
failed.
@FIXME{New node on how to find an archive?}
If you use @value{op-extract} with the @value{op-label} option specified,
-@code{tar} will read an archive label (the tape head has to be positioned
+@command{tar} will read an archive label (the tape head has to be positioned
on it) and print an error if the archive label doesn't match the
@var{archive-name} specified. @var{archive-name} can be any regular
-expression. If the labels match, @code{tar} extracts the archive.
+expression. If the labels match, @command{tar} extracts the archive.
@value{xref-label}.
@FIXME-xref{Matching Format Parameters}@FIXME{fix cross
-references}@samp{tar --list --label} will cause @code{tar} to print the
+references}@samp{tar --list --label} will cause @command{tar} to print the
label.
@FIXME{Program to list all the labels on a tape?}
-@node Using Multiple Tapes, label, Many, Media
+@node Using Multiple Tapes
@section Using Multiple Tapes
@UNREVISED
Often you might want to write a large archive, one larger than will fit
on the actual tape you are using. In such a case, you can run multiple
-@code{tar} commands, but this can be inconvenient, particularly if you
+@command{tar} commands, but this can be inconvenient, particularly if you
are using options like @value{op-exclude} or dumping entire filesystems.
-Therefore, @code{tar} supports multiple tapes automatically.
+Therefore, @command{tar} supports multiple tapes automatically.
-Use @value{op-multi-volume} on the command line, and then @code{tar} will,
+Use @value{op-multi-volume} on the command line, and then @command{tar} will,
when it reaches the end of the tape, prompt for another tape, and
continue the archive. Each tape will have an independent archive, and
can be read without needing the other. (As an exception to this, the
-file that @code{tar} was archiving when it ran out of tape will usually
+file that @command{tar} was archiving when it ran out of tape will usually
be split between the two archives; in this case you need to extract from
the first archive, using @value{op-multi-volume}, and then put in the
-second tape when prompted, so @code{tar} can restore both halves of the
+second tape when prompted, so @command{tar} can restore both halves of the
file.)
-GNU @code{tar} multi-volume archives do not use a truly portable format.
-You need GNU @code{tar} at both end to process them properly.
+@sc{gnu} @command{tar} multi-volume archives do not use a truly portable format.
+You need @sc{gnu} @command{tar} at both end to process them properly.
-When prompting for a new tape, @code{tar} accepts any of the following
+When prompting for a new tape, @command{tar} accepts any of the following
responses:
@table @kbd
@item ?
-Request @code{tar} to explain possible responses
+Request @command{tar} to explain possible responses
@item q
-Request @code{tar} to exit immediately.
+Request @command{tar} to exit immediately.
@item n @var{file name}
-Request @code{tar} to write the next volume on the file @var{file name}.
+Request @command{tar} to write the next volume on the file @var{file name}.
@item !
-Request @code{tar} to run a subshell.
+Request @command{tar} to run a subshell.
@item y
-Request @code{tar} to begin writing the next volume.
+Request @command{tar} to begin writing the next volume.
@end table
(You should only type @samp{y} after you have changed the tape;
-otherwise @code{tar} will write over the volume it just finished.)
+otherwise @command{tar} will write over the volume it just finished.)
-If you want more elaborate behavior than this, give @code{tar} the
+If you want more elaborate behavior than this, give @command{tar} the
@value{op-info-script} option. The file @var{script-name} is expected
to be a program (or shell script) to be run instead of the normal
-prompting procedure. When the program finishes, @code{tar} will
+prompting procedure. When the program finishes, @command{tar} will
immediately begin writing the next volume. The behavior of the
@samp{n} response to the normal tape-change prompt is not available
if you use @value{op-info-script}.
-The method @code{tar} uses to detect end of tape is not perfect, and
+The method @command{tar} uses to detect end of tape is not perfect, and
fails on some operating systems or on some devices. You can use the
-@value{op-tape-length} option if @code{tar} can't detect the end of the
+@value{op-tape-length} option if @command{tar} can't detect the end of the
tape itself. This option selects @value{op-multi-volume} automatically.
The @var{size} argument should then be the usable size of the tape.
But for many devices, and floppy disks in particular, this option is
never required for real, as far as we know.
-The volume number used by @code{tar} in its tape-change prompt
+The volume number used by @command{tar} in its tape-change prompt
can be changed; if you give the @value{op-volno-file} option, then
@var{file-of-number} should be an unexisting file to be created, or else,
a file already containing a decimal number. That number will be used
-as the volume number of the first volume written. When @code{tar} is
+as the volume number of the first volume written. When @command{tar} is
finished, it will rewrite the file with the now-current volume number.
(This does not change the volume number written on a tape label, as
per @value{ref-label}, it @emph{only} affects the number used in
the prompt.)
-If you want @code{tar} to cycle through a series of tape drives, then
+If you want @command{tar} to cycle through a series of tape drives, then
you can use the @samp{n} response to the tape-change prompt. This is
error prone, however, and doesn't work at all with @value{op-info-script}.
-Therefore, if you give @code{tar} multiple @value{op-file} options, then
+Therefore, if you give @command{tar} multiple @value{op-file} options, then
the specified files will be used, in sequence, as the successive volumes
of the archive. Only when the first one in the sequence needs to be
-used again will @code{tar} prompt for a tape change (or run the info
+used again will @command{tar} prompt for a tape change (or run the info
script).
Multi-volume archives
-With @value{op-multi-volume}, @code{tar} will not abort when it cannot
+With @value{op-multi-volume}, @command{tar} will not abort when it cannot
read or write any more data. Instead, it will ask you to prepare a new
volume. If the archive is on a magnetic tape, you should change tapes
now; if the archive is on a floppy disk, you should change disks, etc.
-Each volume of a multi-volume archive is an independent @code{tar}
+Each volume of a multi-volume archive is an independent @command{tar}
archive, complete in itself. For example, you can list or extract any
volume alone; just don't specify @value{op-multi-volume}. However, if one
file in the archive is split across volumes, the only way to extract
the file begins.
For example, let's presume someone has two tape drives on a system
-named @file{/dev/tape0} and @file{/dev/tape1}. For having GNU
-@code{tar} to switch to the second drive when it needs to write the
+named @file{/dev/tape0} and @file{/dev/tape1}. For having @sc{gnu}
+@command{tar} to switch to the second drive when it needs to write the
second tape, and then back to the first tape, etc., just do either of:
@smallexample
* Tape Files:: Tape Files
@end menu
-@node Multi-Volume Archives, Tape Files, Using Multiple Tapes, Using Multiple Tapes
+@node Multi-Volume Archives
@subsection Archives Longer than One Tape or Disk
@cindex Multi-volume archives
@UNREVISED
(provided the @value{op-multi-volume} option is specified), but is
stored on more than one tape or disk.
-When you specify @value{op-multi-volume}, @code{tar} does not report an
+When you specify @value{op-multi-volume}, @command{tar} does not report an
error when it comes to the end of an archive volume (when reading), or
the end of the media (when writing). Instead, it prompts you to load
a new storage volume. If the archive is on a magnetic tape, you
one volume of the media and ends on another), you need to specify
@value{op-multi-volume} to extract it successfully. In this case, you
should load the volume where the archive member starts, and use
-@samp{tar --extract --multi-volume}---@code{tar} will prompt for later
+@samp{tar --extract --multi-volume}---@command{tar} will prompt for later
volumes as it needs them. @xref{extracting archives}, for more
information about extracting archives.
@value{op-info-script} is like @value{op-multi-volume}, except that
-@code{tar} does not prompt you directly to change media volumes when
-a volume is full---instead, @code{tar} runs commands you have stored
+@command{tar} does not prompt you directly to change media volumes when
+a volume is full---instead, @command{tar} runs commands you have stored
in @var{script-name}. For example, this option can be used to eject
cassettes, or to broadcast messages such as @samp{Someone please come
change my tape} when performing unattended backups. When @var{script-name}
-is done, @code{tar} will assume that the media has been changed.
+is done, @command{tar} will assume that the media has been changed.
Multi-volume archives can be modified like any other archive. To add
files to a multi-volume archive, you need to only mount the last
other operations, you need to use the entire archive.
If a multi-volume archive was labeled using @value{op-label}
-(@value{pxref-label}) when it was created, @code{tar} will not
+(@value{pxref-label}) when it was created, @command{tar} will not
automatically label volumes which are added later. To label subsequent
volumes, specify @value{op-label} again in conjunction with the
@value{op-append}, @value{op-update} or @value{op-concatenate} operation.
@end table
Beware that there is @emph{no} real standard about the proper way, for a
-@code{tar} archive, to span volume boundaries. If you have a multi-volume
-created by some vendor's @code{tar}, there is almost no chance you could
-read all the volumes with GNU @code{tar}. The converse is also true:
-you may not expect multi-volume archives created by GNU @code{tar} to
-be fully recovered by vendor's @code{tar}. Since there is little chance
-that, in mixed system configurations, some vendor's @code{tar} will work on
-another vendor's machine, and there is a great chance that GNU @code{tar}
-will work on most of them, your best bet is to install GNU @code{tar}
+@command{tar} archive, to span volume boundaries. If you have a multi-volume
+created by some vendor's @command{tar}, there is almost no chance you could
+read all the volumes with @sc{gnu} @command{tar}. The converse is also true:
+you may not expect multi-volume archives created by @sc{gnu} @command{tar} to
+be fully recovered by vendor's @command{tar}. Since there is little chance
+that, in mixed system configurations, some vendor's @command{tar} will work on
+another vendor's machine, and there is a great chance that @sc{gnu} @command{tar}
+will work on most of them, your best bet is to install @sc{gnu} @command{tar}
on all machines between which you know exchange of files is possible.
-@node Tape Files, , Multi-Volume Archives, Using Multiple Tapes
+@node Tape Files
@subsection Tape Files
@UNREVISED
option when reading an archive, it checks to make sure the label on the
tape matches the one you give. @value{xref-label}.
-When @code{tar} writes an archive to tape, it creates a single
+When @command{tar} writes an archive to tape, it creates a single
tape file. If multiple archives are written to the same tape, one
after the other, they each get written as separate tape files. When
extracting, it is necessary to position the tape at the right place
-before running @code{tar}. To do this, use the @code{mt} command.
-For more information on the @code{mt} command and on the organization
+before running @command{tar}. To do this, use the @command{mt} command.
+For more information on the @command{mt} command and on the organization
of tapes into a sequence of tape files, see @ref{mt}.
People seem to often do:
or such, for pushing a common date in all volumes or an archive set.
-@node label, verify, Using Multiple Tapes, Media
+@node label
@section Including a Label in the Archive
@cindex Labeling an archive
@cindex Labels on the archive media
Create archive with volume name @var{name}.
@end table
-This option causes @code{tar} to write out a @dfn{volume header} at
+This option causes @command{tar} to write out a @dfn{volume header} at
the beginning of the archive. If @value{op-multi-volume} is used, each
volume of the archive will have a volume header of @samp{@var{name}
Volume @var{n}}, where @var{n} is 1 for the first volume, 2 for the
@FIXME-xref{Multi-Volume Archives, for information on creating multiple
volume archives.}
-If you list or extract an archive using @value{op-label}, @code{tar} will
+If you list or extract an archive using @value{op-label}, @command{tar} will
print an error if the archive label doesn't match the @var{archive-label}
specified, and will then not list nor extract the archive. In those cases,
@var{archive-label} argument is interpreted as a globbing-style pattern
which must match the actual magnetic volume label. @xref{exclude}, for
a precise description of how match is attempted@footnote{Previous versions
-of @code{tar} used full regular expression matching, or before that, only
+of @command{tar} used full regular expression matching, or before that, only
exact string matching, instead of wildcard matchers. We decided for the
-sake of simplicity to use a uniform matching device through @code{tar}.}.
+sake of simplicity to use a uniform matching device through @command{tar}.}.
If the switch @value{op-multi-volume} is being used, the volume label
matcher will also suffix @var{archive-label} by @w{@samp{ Volume [1-9]*}}
if the initial match fails, before giving up. Since the volume numbering
under that name anymore.
To find out an archive's label entry (or to find out if an archive has
-a label at all), use @samp{tar --list --verbose}. @code{tar} will print the
+a label at all), use @samp{tar --list --verbose}. @command{tar} will print the
label first, and then print archive member information, as in the
example below:
@end example
Also note that each label has its own date and time, which corresponds
-to when GNU @code{tar} initially attempted to write it, often soon
-after the operator launches @code{tar} or types the carriage return
+to when @sc{gnu} @command{tar} initially attempted to write it, often soon
+after the operator launches @command{tar} or types the carriage return
telling that the next tape is ready. Comparing date labels does give
an idea of tape throughput only if the delays for rewinding tapes
and the operator switching them were negligible, which is usually
@FIXME{was --volume}
-@node verify, Write Protection, label, Media
+@node verify
@section Verifying Data as It is Stored
@cindex Verifying a write operation
@cindex Double-checking a write operation
Attempt to verify the archive after writing.
@end table
-This option causes @code{tar} to verify the archive after writing it.
+This option causes @command{tar} to verify the archive after writing it.
Each volume is checked after it is written, and any discrepancies
are recorded on the standard error output.
cannot be verified.
You can insure the accuracy of an archive by comparing files in the
-system with archive members. @code{tar} can compare an archive to the
+system with archive members. @command{tar} can compare an archive to the
file system as the archive is being written, to verify a write
operation, or can compare a previously written archive, to insure that
it is up to date.
To check for discrepancies in an archive immediately after it is
written, use the @value{op-verify} option in conjunction with
the @value{op-create} operation. When this option is
-specified, @code{tar} checks archive members against their counterparts
+specified, @command{tar} checks archive members against their counterparts
in the file system, and reports discrepancies on the standard error. In
multi-volume archives, each volume is verified after it is written,
before the next volume is written.
archive with what is on your disks, while the @value{op-verify} option is
really for checking if the physical contents agree and if the recording
media itself is of dependable quality. So, for the @value{op-verify}
-operation, @code{tar} tries to defeat all in-memory cache pertaining to
+operation, @command{tar} tries to defeat all in-memory cache pertaining to
the archive, while it lets the speed optimization undisturbed for the
@value{op-compare} option. If you nevertheless use @value{op-compare} for
media verification, you may have to defeat the in-memory cache yourself,
not say that drivers unable to detect all cases are necessarily flawed,
as long as programming is concerned.
-@node Write Protection, , verify, Media
+@node Write Protection
@section Write Protection
Almost all tapes and diskettes, and in a few rare cases, even disks can
which can be removed from the center of a tape reel, or some other
changeable feature.
-@node Index, , Media, Top
+@node Index
@unnumbered Index
@printindex cp
projects / chaz / tar / commitdiff
