tar progress
Typically, tar performs most operations without reporting any
information to the user except error messages. When using tar
with many options, particularly ones with complicated or
difficult-to-predict behavior, it is possible to make serious mistakes.
tar provides several options that make observing tar
easier. These options cause 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
archive, however, you may need more information than just an error
message in order to solve the problem. The following options can be
helpful diagnostic tools.
Normally, the --list (-t) 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 --verbose (-v) option causes
tar to print the name of each file or archive member as it
is processed. This and the other options which make tar print
status information can be useful in monitoring tar.
With --create (-c) or --extract (--get, -x), --verbose (-v) used once
just prints the names of the files or members as they are processed.
Using it twice causes tar to print a longer listing (reminiscent
of `ls -l') for each member. Since --list (-t) already prints
the names of the members, --verbose (-v) used once with --list (-t)
causes tar to print an `ls -l' type listing of the files
in the archive. The following examples both extract members with
long list output:
$ tar --extract --file=archive.tar --verbose --verbose $ tar xvv archive.tar
Verbose output appears on the standard output except when an archive is
being written to the standard output, as with `tar --create
--file=- --verbose' (`tar cfv -', or even `tar cv'---if the
installer let standard output be the default archive). In that case
tar writes verbose output to the standard error stream.
The --totals option--which is only meaningful when used with
--create (-c)---causes tar to print the total
amount written to the archive, after it has been fully created.
The --checkpoint option prints an occasional message
as 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
--block-number (-R), but do want visual confirmation that tar
is actually making forward progress.
@FIXME{There is some confusion here. It seems that -R once wrote a message at `every' record read or written.}
The --show-omitted-dirs option, when reading an archive--with --list (-t) or --extract (--get, -x), for example--causes a message to be printed for each directory in the archive which is skipped. This happens regardless of the reason for skipping: the directory might not have been named on the command line (implicitly or explicitly), it might be excluded by the use of the --exclude=pattern option, or some other reason.
If --block-number (-R) is used, 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 --block-number (-R)
is used. Note that GNU tar drains the archive before exiting when
reading the archive from a pipe.
This option is especially useful when reading damaged archives, since it helps pinpoint the damaged sections. It can also be used with --list (-t) when listing a file-system backup tape, allowing you to choose among several backup tapes when retrieving a file later, in favor of the tape where the file appears earliest (closest to the front of the tape). @FIXME-xref{when the node name is set and the backup section written}.
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