performing potentially destructive options, such as overwriting files.
@xref{interactive}.
+@opsummary{--keep-directory-symlink}
+@item --keep-directory-symlink
+
+This option changes the behavior of tar when it encounters a symlink
+with the same name as the directory that it is about to extract. By
+default, in this case tar would first remove the symlink and then
+proceed extracting the directory.
+
+The @option{--keep-directory-symlink} option disables this behavior
+and instructs tar to follow symlinks to directories when extracting
+from the archive.
+
+It is mainly intended to provide compatibility with the Slackware
+installation scripts.
+
@opsummary{keep-newer-files}
@item --keep-newer-files
directories that are on different file systems from the current
directory.
+@opsummary{one-top-level}
+@item --one-top-level[=@var{dir}]
+Tells @command{tar} to create a new directory beneath the extraction directory
+(or the one passed to @option{-C}) and use it to guard against
+tarbombs. In the absence of @var{dir} argument, the name of the new directory
+will be equal to the base name of the archive (file name minus the
+archive suffix, if recognized). Any member names that do not begin
+with that directory name (after
+transformations from @option{--transform} and
+@option{--strip-components}) will be prefixed with it. Recognized
+file name suffixes are @samp{.tar}, and any compression suffixes
+recognizable by @xref{--auto-compress}.
+
@opsummary{overwrite}
@item --overwrite
@noindent
Notice, that this option outputs only one line. The example output
-above has been split to fit page boundaries.
+above has been split to fit page boundaries. @xref{defaults}.
@opsummary{show-omitted-dirs}
@item --show-omitted-dirs
Instructs @command{tar} to mention the directories it is skipping when
operating on a @command{tar} archive. @xref{show-omitted-dirs}.
+@opsummary{show-snapshot-field-ranges}
+@item --show-snapshot-field-ranges
+
+Displays the range of values allowed by this version of @command{tar}
+for each field in the snapshot file, then exits successfully.
+@xref{Snapshot Files}.
+
@opsummary{show-transformed-names}
@opsummary{show-stored-names}
@item --show-transformed-names
@smallexample
tar (GNU tar) @value{VERSION}
-Copyright (C) 2013 Free Software Foundation, Inc.
+Copyright (C) 2013-2014 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
@end smallexample
The @samp{%s} and @samp{%u} in the above example are
-@dfn{meta-characters}. The @samp{%s} meta-character is replaced with
+@dfn{format specifiers}. The @samp{%s} specifier is replaced with
the @dfn{type} of the checkpoint: @samp{write} or
@samp{read} (or a corresponding translated version in locales other
-than @acronym{POSIX}). The @samp{%u} meta-character is replaced with
+than @acronym{POSIX}). The @samp{%u} specifier is replaced with
the ordinal number of the checkpoint. Thus, the above example could
produce the following output when used with the @option{--create}
option:
tar: Hit write checkpoint #30
@end smallexample
-Aside from meta-character expansion, the message string is subject to
+The complete list of available format specifiers follows. Some of
+them can take optional arguments. These arguments, if given, are
+supplied in curly braces between the percent sign and the specifier
+letter.
+
+@table @samp
+@item %s
+Print type of the checkpoint (@samp{write} or @samp{read}).
+
+@item %u
+Print number of the checkpoint.
+
+@item %@{r,w,d@}T
+Print number of bytes transferred so far and approximate transfer
+speed. Optional arguments supply prefixes to be used before number
+of bytes read, written and deleted, correspondingly. If absent,
+they default to @samp{R}. @samp{W}, @samp{D}. Any or all of them can
+be omitted, so, that e.g. @samp{%@{@}T} means to print corresponding
+statistics without any prefixes. Any surplus arguments, if present,
+are silently ignored.
+
+@example
+$ @kbd{tar --delete -f f.tar --checkpoint-action=echo="#%u: %T" main.c}
+tar: #1: R: 0 (0B, 0B/s),W: 0 (0B, 0B/s),D: 0
+tar: #2: R: 10240 (10KiB, 19MiB/s),W: 0 (0B, 0B/s),D: 10240
+@end example
+
+@noindent
+See also the @samp{totals} action, described below.
+
+@item %@{@var{fmt}@}t
+Output current local time using @var{fmt} as format for @command{strftime}
+(@pxref{strftime, strftime,,strftime(3), strftime(3) man page}). The
+@samp{@{@var{fmt}@}} part is optional. If not present, the default
+format is @samp{%c}, i.e. the preferred date and time representation
+for the current locale.
+
+@item %@{@var{n}@}*
+Pad output with spaces to the @var{n}th column. If the
+@samp{@{@var{n}@}} part is omitted, the current screen width
+is assumed.
+
+@item %@var{c}
+This is a shortcut for @samp{%@{%Y-%m-%d %H:%M:%S@}t: %ds, %@{read,wrote@}T%*\r},
+intended mainly for use with @samp{ttyout} action (see below).
+@end table
+
+Aside from format expansion, the message string is subject to
@dfn{unquoting}, during which the backslash @dfn{escape sequences} are
replaced with their corresponding @acronym{ASCII} characters
(@pxref{escape sequences}). E.g. the following action will produce an
line, overwriting any previous message:
@smallexample
---checkpoint-action="ttyout=\rHit %s checkpoint #%u"
+--checkpoint-action="ttyout=Hit %s checkpoint #%u%*\r"
+@end smallexample
+
+@noindent
+Notice the use of @samp{%*} specifier to clear out any eventual
+remains of the prior output line. As as more complex example,
+consider this:
+
+@smallexample
+--checkpoint-action=ttyout='%@{%Y-%m-%d %H:%M:%S@}t (%d sec): #%u, %T%*\r'
@end smallexample
+@noindent
+This prints the current local time, number of seconds expired since
+tar was started, the checkpoint ordinal number, transferred bytes and
+average computed I/O speed.
+
@cindex @code{dot}, checkpoint action
Another available checkpoint action is @samp{dot} (or @samp{.}). It
instructs @command{tar} to print a single dot on the standard listing
be abbreviated by placing a dot in front of the checkpoint frequency,
as shown in the previous section.
+@cindex @code{totals}, checkpoint action
+The @samp{totals} action prints the total number of bytes transferred
+so far. The format of the data is the same as for the
+@option{--totals} option (@pxref{totals}). See also @samp{%T} format
+specifier of the @samp{echo} or @samp{ttyout} action.
+
@cindex @code{sleep}, checkpoint action
Yet another action, @samp{sleep}, pauses @command{tar} for a specified
amount of seconds. The following example will stop for 30 seconds at each
This means that @command{tar} first tried to decompress
@file{archive.Z} using @command{compress}, and, when that
failed, switched to @command{gzip}.
+@kwindex record-size
+@cindex @samp{Record size = %lu blocks}, warning message
+@item record-size
+@samp{Record size = %lu blocks}
@end table
@subheading Keywords controlling incremental extraction:
@end group
@end smallexample
-@noindent
-@xopindex{directory, using in @option{--files-from} argument}
-Notice that the option parsing algorithm used with @option{-T} is
-stricter than the one used by shell. Namely, when specifying option
-arguments, you should observe the following rules:
-
-@itemize @bullet
-@item
-When using short (single-letter) option form, its argument must
-immediately follow the option letter, without any intervening
-whitespace. For example: @code{-Cdir}.
-
-@item
-When using long option form, the option argument must be separated
-from the option by a single equal sign. No whitespace is allowed on
-any side of the equal sign. For example: @code{--directory=dir}.
-
-@item
-For both short and long option forms, the option argument can be given
-on the next line after the option name, e.g.:
-
-@smallexample
-@group
---directory
-dir
-@end group
-@end smallexample
-
-@noindent
-and
-
-@smallexample
-@group
--C
-dir
-@end group
-@end smallexample
-@end itemize
-
@opindex add-file
If you happen to have a file whose name starts with @samp{-},
precede it with @option{--add-file} option to prevent it from
This example uses short options for typographic reasons, to avoid
very long lines.
-@GNUTAR is able to automatically detect @code{NUL}-terminated file lists, so
-it is safe to use them even without the @option{--null} option. In
-this case @command{tar} will print a warning and continue reading such
-a file as if @option{--null} were actually given:
+@GNUTAR is tries to automatically detect @code{NUL}-terminated file
+lists, so in many cases it is safe to use them even without the
+@option{--null} option. In this case @command{tar} will print a
+warning and continue reading such a file as if @option{--null} were
+actually given:
@smallexample
@group
record size on itself. When this is the case, and a non-standard
record size 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, @command{tar} cannot figure
-out the record size itself. On most of those, you can specify a
-blocking factor (with @option{--blocking-factor}) larger than the
-actual blocking factor, and then use the @option{--read-full-records}
-(@option{-B}) option. (If you specify a blocking factor with
-@option{--blocking-factor} and don't use the
-@option{--read-full-records} 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
+normally@footnote{If this message is not needed, you can turn it off
+using the @option{--warning=no-record-size} option.}. On some tape
+devices, however, @command{tar} cannot figure out the record size
+itself. On most of those, you can specify a blocking factor (with
+@option{--blocking-factor}) larger than the actual blocking factor,
+and then use the @option{--read-full-records} (@option{-B}) option.
+(If you specify a blocking factor with @option{--blocking-factor} and
+don't use the @option{--read-full-records} 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
@option{--blocking-factor} when reading, because @command{tar} cannot
figure it out. In any case, use @option{--list} (@option{-t}) before
doing any extractions to see whether @command{tar} is reading the archive
projects / chaz / tar / blobdiff