Appendices
+* Changes::
* Genfile::
* Snapshot Files::
* Free Software Needs Free Documentation::
* Definitions:: Some Definitions
* What tar Does:: What @command{tar} Does
* Naming tar Archives:: How @command{tar} Archives are Named
-* Current status:: Current development status of @GNUTAR{}
* Authors:: @GNUTAR{} Authors
* Reports:: Reporting bugs or suggestions
Copying This Manual
+* Free Software Needs Free Documentation::
* GNU Free Documentation License:: License for copying this manual
@end detailmenu
* Definitions:: Some Definitions
* What tar Does:: What @command{tar} Does
* Naming tar Archives:: How @command{tar} Archives are Named
-* Current status:: Current development status of @GNUTAR{}
* Authors:: @GNUTAR{} Authors
* Reports:: Reporting bugs or suggestions
@end menu
this manual, we consistently refer to ``archives'' and ``archive
members'' to make learning to use @command{tar} easier for novice users.
-@node Current status
-@section Current development status of @GNUTAR{}
-
-@GNUTAR{} is currently in the process of active development, whose
-primary aims are:
-
-@itemize @bullet
-@item Improve compatibility between @GNUTAR{} and other @command{tar}
-implementations.
-@item Switch to using @acronym{POSIX} archives.
-@item Revise sparse file handling and multiple volume processing.
-@item Merge with the @acronym{GNU} @code{paxutils} project.
-@end itemize
-
-Some of these aims are already attained, while others are still
-being worked upon. From the point of view of an end user, the
-following issues need special mentioning:
-
-@table @asis
-@item Use of short option @option{-o}.
-
-Earlier versions of @GNUTAR{} understood @option{-o} command line
-option as a synonym for @option{--old-archive}.
-
-@GNUTAR{} starting from version 1.13.90 understands this option as
-a synonym for @option{--no-same-owner}. This is compatible with
-UNIX98 @command{tar} implementations.
-
-However, to facilitate transition, @option{-o} option retains its
-old semantics when it is used with one of archive-creation commands.
-Users are encouraged to use @option{--format=oldgnu} instead.
-
-It is especially important, since versions of @acronym{GNU} Automake
-up to and including 1.8.4 invoke tar with this option to produce
-distribution tarballs. @xref{Formats,v7}, for the detailed discussion
-of this issue and its implications.
-
-Future versions of @GNUTAR{} will understand @option{-o} only as a
-synonym for @option{--no-same-owner}.
-
-@item Use of short option @option{-l}
-
-Earlier versions of @GNUTAR{} understood @option{-l} option as a
-synonym for @option{--one-file-system}. Such usage is deprecated.
-For compatibility with other implementations future versions of
-@GNUTAR{} will understand this option as a synonym for
-@option{--check-links}.
-
-@item Use of options @option{--portability} and @option{--old-archive}
-
-These options are deprecated. Please use @option{--format=v7} instead.
-
-@item Use of option @option{--posix}
-
-This option is deprecated. Please use @option{--format=posix} instead.
-@end table
-
@node Authors
@section @GNUTAR{} Authors
@option{--check-links}. However, current release still retains the old
semantics for @option{-l}.
-@xref{Current status}, for more information.
+@xref{Changes}, for more information.
@opindex compress, summary
@opindex uncompress, summary
with previous versions of @GNUTAR{}, and will be
removed in the future releases.
-@xref{Current status}, for more information.
+@xref{Changes}, for more information.
@opindex occurrence, summary
@item --occurrence[=@var{number}]
The future versions of @GNUTAR{} will use @option{-l} as
a synonym for @option{--check-links}.
-@xref{Current status}, for more information.
+@xref{Changes}, for more information.
@opindex overwrite, summary
@item --overwrite
is retained for compatibility with the earlier versions of GNU
@command{tar}, and will be changed in future releases.
-@xref{Current status}, for more information.
+@xref{Changes}, for more information.
@item -m
@cindex large values
@cindex future time stamps
@cindex negative time stamps
-
-@acronym{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. @GNUTAR{}
-generates @acronym{POSIX} representations when possible, but for values
-outside the @acronym{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 @acronym{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 @acronym{POSIX}
-@command{tar} format cannot represent them.
-
-Portable archives should avoid time stamps from the future. @acronym{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 @acronym{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. @GNUTAR{} 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.
+@UNREVISED{}
+
+The above sections suggest to use @samp{oldest possible} archive
+format if in doubt. However, sometimes it is not possible. If you
+attempt to archive a file whose metadata cannot be represented using
+required format, @GNUTAR{} will print error message and ignore such a
+file. You will than have to switch to a format that is able to
+handle such values. The format summary table (@pxref{Formats}) will
+help you to do so.
+
+In particular, when trying to archive files larger than 8GB or with
+timestamps not in the range 1970-01-01 00:00:00 through 2242-03-16
+12:56:31 @sc{utc}, you will have to chose between @acronym{GNU} and
+@acronym{POSIX} archive formats. When considering which format to
+choose, bear in mind that the @acronym{GNU} format uses
+two's-complement base-256 notation to stores values that do not fit
+into standard @acronym{ustar} range. Such archives can generally be
+read only by a @GNUTAR{} implementation. Moreover, they sometimes
+cannot be correctly restored on another hosts even by @GNUTAR{}. For
+example, using two's complement representation for negative time
+stamps that assumes a signed 32-bit @code{time_t} generates archives
+that are not portable to hosts with differing @code{time_t}
+representations.
+
+On the other hand, @acronym{POSIX} archives, generally speaking, can
+be extracted by any tar implementation that understands older
+@acronym{ustar} format. The only exception are files larger than 8GB.
+
+@FIXME{Describe how @acronym{POSIX} archives are extracted by non
+POSIX-aware tars.}
@node Compression
@section Using Less Space through Compression
which can be removed from the center of a tape reel, or some other
changeable feature.
-@node Free Software Needs Free Documentation
-@appendix Free Software Needs Free Documentation
-@include freemanuals.texi
+@node Changes
+@appendix Changes
+
+This appendix lists some important user-visible changes between
+version @GNUTAR{} @value{VERSION} and previous versions. An up-to-date
+version of this document is available at
+@uref{http://www.gnu.org/@/software/@/tar/manual/changes.html,the
+@GNUTAR{} documentation page}.
+
+@table @asis
+@item Use of short option @option{-o}.
+
+Earlier versions of @GNUTAR{} understood @option{-o} command line
+option as a synonym for @option{--old-archive}.
+
+@GNUTAR{} starting from version 1.13.90 understands this option as
+a synonym for @option{--no-same-owner}. This is compatible with
+UNIX98 @command{tar} implementations.
+
+However, to facilitate transition, @option{-o} option retains its
+old semantics when it is used with one of archive-creation commands.
+Users are encouraged to use @option{--format=oldgnu} instead.
+
+It is especially important, since versions of @acronym{GNU} Automake
+up to and including 1.8.4 invoke tar with this option to produce
+distribution tarballs. @xref{Formats,v7}, for the detailed discussion
+of this issue and its implications.
+
+Future versions of @GNUTAR{} will understand @option{-o} only as a
+synonym for @option{--no-same-owner}.
+
+@item Use of short option @option{-l}
+
+Earlier versions of @GNUTAR{} understood @option{-l} option as a
+synonym for @option{--one-file-system}. Such usage is deprecated.
+For compatibility with other implementations future versions of
+@GNUTAR{} will understand this option as a synonym for
+@option{--check-links}.
+
+@item Use of options @option{--portability} and @option{--old-archive}
+
+These options are deprecated. Please use @option{--format=v7} instead.
+
+@item Use of option @option{--posix}
+
+This option is deprecated. Please use @option{--format=posix} instead.
+@end table
@node Genfile
@appendix Genfile
@appendix Format of the Incremental Snapshot Files
@include snapshot.texi
+@node Free Software Needs Free Documentation
+@appendix Free Software Needs Free Documentation
+@include freemanuals.texi
+
@node Copying This Manual
@appendix Copying This Manual
projects / chaz / tar / commitdiff
