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@@ -11355,15 +11355,16 @@ will usually see lots of spurious messages.
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@cindex Labeling an archive
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@cindex Labels on the archive media
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@cindex Labeling multi-volume archives
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-@UNREVISED
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@opindex label
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To avoid problems caused by misplaced paper labels on the archive
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-media, you can include a @dfn{label} entry---an archive member which
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-contains the name of the archive---in the archive itself. Use the
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+media, you can include a @dfn{label} entry --- an archive member which
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+contains the name of the archive --- in the archive itself. Use the
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@option{--label=@var{archive-label}} (@option{-V @var{archive-label}})
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-option in conjunction with the @option{--create} operation to include
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-a label entry in the archive as it is being created.
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+option@footnote{Until version 1.10, that option was called
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+@option{--volume}, but is not available under that name anymore.} in
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+conjunction with the @option{--create} operation to include a label
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+entry in the archive as it is being created.
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@table @option
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@item --label=@var{archive-label}
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@@ -11402,7 +11403,7 @@ V--------- 0 0 0 1992-03-07 12:01 iamalabel--Volume Header--
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However, @option{--list} option will cause listing entire
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contents of the archive, which may be undesirable (for example, if the
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archive is stored on a tape). You can request checking only the volume
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-by specifying @option{--test-label} option. This option reads only the
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+label by specifying @option{--test-label} option. This option reads only the
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first block of an archive, so it can be used with slow storage
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devices. For example:
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@@ -11413,16 +11414,35 @@ iamalabel
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@end group
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@end smallexample
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- If @option{--test-label} is used with a single command line
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-argument, @command{tar} compares the volume label with the
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-argument. It exits with code 0 if the two strings match, and with code
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-2 otherwise. In this case no output is displayed. For example:
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+ If @option{--test-label} is used with one or more command line
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+arguments, @command{tar} compares the volume label with each
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+argument. It exits with code 0 if a match is found, and with code 1
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+otherwise@footnote{Note that @GNUTAR{} versions up to 1.23 indicated
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+mismatch with an exit code 2 and printed a spurious diagnostics on
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+stderr.}. No output is displayed, unless you also used the
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+@option{--verbose} option. For example:
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+
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+@smallexample
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+@group
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+$ @kbd{tar --test-label --file=iamanarchive 'iamalabel'}
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+@result{} 0
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+$ @kbd{tar --test-label --file=iamanarchive 'alabel'}
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+@result{} 1
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+@end group
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+@end smallexample
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+
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+ When used with the @option{--verbose} option, @command{tar}
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+prints the actual volume label (if any), and a verbose diagnostics in
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+case of a mismatch:
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@smallexample
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@group
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-$ @kbd{tar --test-label --file=iamanarchive 'iamalable'}
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+$ @kbd{tar --test-label --verbose --file=iamanarchive 'iamalabel'}
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+iamalabel
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@result{} 0
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-$ @kbd{tar --test-label --file=iamanarchive 'iamalable' alabel}
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+$ @kbd{tar --test-label --verbose --file=iamanarchive 'alabel'}
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+iamalabel
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+tar: Archive label mismatch
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@result{} 1
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@end group
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@end smallexample
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@@ -11462,9 +11482,6 @@ up. Since the volume numbering is automatically added in labels at
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creation time, it sounded logical to equally help the user taking care
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of it when the archive is being read.
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- The @option{--label} was once called @option{--volume}, but is not
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-available under that name anymore.
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-
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You can also use @option{--label} to get a common information on
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all tapes of a series. For having this information different in each
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series created through a single script used on a regular basis, just
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@@ -11478,13 +11495,19 @@ $ @kbd{tar --create --file=/dev/tape --multi-volume \
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@end group
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@end smallexample
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- Also note that each label has its own date and time, which corresponds
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-to when @GNUTAR{} initially attempted to write it,
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+ Some more notes about volume labels:
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+
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+@itemize @bullet
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+@item Each label has its own date and time, which corresponds
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+to the time when @GNUTAR{} initially attempted to write it,
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often soon after the operator launches @command{tar} or types the
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-carriage return telling that the next tape is ready. Comparing date
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-labels does give an idea of tape throughput only if the delays for
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-rewinding tapes and the operator switching them were negligible, which
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-is usually not the case.
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+carriage return telling that the next tape is ready.
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+
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+@item Comparing date labels to get an idea of tape throughput is
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+unreliable. It gives correct results only if the delays for rewinding
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+tapes and the operator switching them were negligible, which is
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+usually not the case.
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+@end itemize
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@node verify
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@section Verifying Data as It is Stored
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Sergey Poznyakoff