tar.texi

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@cindex listing member and file names
@anchor{listing member and file names}
It is important to notice that the output of @kbd{tar --list
--verbose} does not necessarily match that produced by @kbd{tar
--create --verbose} while creating the archive.  It is because
@GNUTAR{}, unless told explicitly not to do so, removes some directory
prefixes from file names before storing them in the archive
(@xref{absolute}, for more information).  In other
words, in verbose mode @GNUTAR{} shows @dfn{file names} when creating
an archive and @dfn{member names} when listing it.  Consider this
example:

@smallexample
@group
$ @kbd{tar cfv archive /etc/mail}
tar: Removing leading `/' from member names
/etc/mail/
/etc/mail/sendmail.cf
/etc/mail/aliases
$ @kbd{tar tf archive}
etc/mail/
etc/mail/sendmail.cf
etc/mail/aliases
@end group
@end smallexample

@opindex show-stored-names
  This default behavior can sometimes be inconvenient.  You can force
@GNUTAR{} show member names when creating archive by supplying
@option{--show-stored-names} option.

@table @option
@item --show-stored-names
Print member (as opposed to @emph{file}) names when creating the archive.
@end table

@cindex File name arguments, using @option{--list} with
@xopindex{list, using with file name arguments}
You can specify one or more individual member names as arguments when
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}.

Because @command{tar} preserves file names, these must be specified as
they appear in the archive (i.e., relative to the directory from which
the archive was created).  Therefore, it is essential when specifying
member names to @command{tar} that you give the exact member names.
For example, @w{@kbd{tar --list --file=bfiles.tar 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 names @file{birds} and @file{./birds} name
the same file, @emph{member} names by default are compared verbatim.

However, @w{@kbd{tar --list --file=bfiles.tar baboon}} would respond
with @file{baboon}, because this exact member name is in the archive file
@file{bfiles.tar}.  If you are not sure of the exact file name,
use @dfn{globbing patterns}, for example:

@smallexample
$ @kbd{tar --list --file=bfiles.tar --wildcards '*b*'}
@end smallexample

@noindent
will list all members whose name contains @samp{b}.  @xref{wildcards},
for a detailed discussion of globbing patterns and related
@command{tar} command line options.

@menu
* list dir::
@end menu

@node list dir
@unnumberedsubsec Listing the Contents of a Stored Directory

To get information about the contents of an archived directory,
use the directory name as a file name argument in conjunction with
@option{--list} (@option{-t}).  To find out file attributes, include the
@option{--verbose} (@option{-v}) option.

For example, to find out about files in the directory @file{practice}, in
the archive file @file{music.tar}, type:

@smallexample
$ @kbd{tar --list --verbose --file=music.tar practice}
@end smallexample

@command{tar} responds:

@smallexample
drwxrwxrwx myself user 0 1990-05-31 21:49 practice/
-rw-r--r-- myself user 42 1990-05-21 13:29 practice/blues
-rw-r--r-- myself user 62 1990-05-23 10:55 practice/folk
-rw-r--r-- myself user 40 1990-05-21 13:30 practice/jazz
-rw-r--r-- myself user 10240 1990-05-31 21:49 practice/collection.tar
@end smallexample

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
@section How to Extract Members from an Archive
@UNREVISED
@cindex Extraction
@cindex Retrieving files from an archive
@cindex Resurrecting files from an archive

@opindex extract
Creating an archive is only half the job---there is no point in storing
files in an archive if you can't retrieve them.  The act of retrieving
members from an archive so they can be used and manipulated as
unarchived files again is called @dfn{extraction}.  To extract files
from an archive, use the @option{--extract} (@option{--get} or
@option{-x}) operation.  As with @option{--create}, specify the name
of the archive with @option{--file} (@option{-f}) option. Extracting
an archive does not modify the archive in any way; you can extract it
multiple times if you want or need to.

Using @option{--extract}, you can extract an entire archive, or specific
files.  The files can be directories containing other files, or not.  As
with @option{--create} (@option{-c}) and @option{--list} (@option{-t}), you may use the short or the
long form of the operation without affecting the performance.

@menu
* extracting archives::
* extracting files::
* extract dir::
* extracting untrusted archives::
* failing commands::
@end menu

@node extracting archives
@subsection Extracting an Entire Archive

To extract an entire archive, specify the archive file name only, with
no individual file names as arguments.  For example,

@smallexample
$ @kbd{tar -xvf collection.tar}
@end smallexample

@noindent
produces this:

@smallexample
-rw-r--r-- me user     28 1996-10-18 16:31 jazz
-rw-r--r-- me user     21 1996-09-23 16:44 blues
-rw-r--r-- me user     20 1996-09-23 16:44 folk
@end smallexample

@node extracting files
@subsection Extracting Specific Files

To extract specific archive members, give their exact member names as
arguments, as printed by @option{--list} (@option{-t}).  If you had
mistakenly deleted one of the files you had placed in the archive
@file{collection.tar} earlier (say, @file{blues}), you can extract it
from the archive without changing the archive's structure.  Its
contents will be identical to the original file @file{blues} that you
deleted.

First, make sure you are in the @file{practice} directory, and list the
files in the directory.  Now, delete the file, @samp{blues}, and list
the files in the directory again.

You can now extract the member @file{blues} from the archive file
@file{collection.tar} like this:

@smallexample
$ @kbd{tar --extract --file=collection.tar blues}
@end smallexample

@noindent
If you list the files in the directory again, you will see that the file
@file{blues} has been restored, with its original permissions, data
modification times, and owner.@footnote{This is only accidentally
true, but not in general.  Whereas modification times are always
restored, in most cases, one has to be root for restoring the owner,
and use a special option for restoring permissions.  Here, it just
happens that the restoring user is also the owner of the archived
members, and that the current @code{umask} is compatible with original
permissions.}  (These parameters will be identical to those which
the file had when you originally placed it in the archive; any changes
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 @command{tar} with
@option{--list} (@option{-t}).

Remember that as with other operations, specifying the exact member
name is important.  @w{@kbd{tar --extract --file=bfiles.tar birds}}
will fail, because there is no member named @file{birds}.  To extract
the member named @file{./birds}, you must specify @w{@kbd{tar
--extract --file=bfiles.tar ./birds}}.  If you don't remember the
exact member names, use @option{--list} (@option{-t}) option
(@pxref{list}).  You can also extract those members that match a
specific @dfn{globbing pattern}.  For example, to extract from
@file{bfiles.tar} all files that begin with @samp{b}, no matter their
directory prefix, you could type:

@smallexample
$ @kbd{tar -x -f bfiles.tar --wildcards --no-anchored 'b*'}
@end smallexample

@noindent
Here, @option{--wildcards} instructs @command{tar} to treat
command line arguments as globbing patterns and @option{--no-anchored}
informs it that the patterns apply to member names after any @samp{/}
delimiter.  The use of globbing patterns is discussed in detail in
@xref{wildcards}.

You can extract a file to standard output by combining the above options
with the @option{--to-stdout} (@option{-O}) option (@pxref{Writing to Standard
Output}).

If you give the @option{--verbose} option, then @option{--extract}
will print the names of the archive members as it extracts them.

@node extract dir
@subsection Extracting Files that are Directories

Extracting directories which are members of an archive is similar to
extracting other files.  The main difference to be aware of is that if
the extracted directory has the same name as any directory already in
the working directory, then files in the extracted directory will be
placed into the directory of the same name.  Likewise, if there are
files in the pre-existing directory with the same names as the members
which you extract, the files from the extracted archive will replace
the files already in the working directory (and possible
subdirectories).  This will happen regardless of whether or not the
files in the working directory were more recent than those extracted
(there exist, however, special options that alter this behavior
@pxref{Writing}).

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, @command{tar} will create the directory.

We can demonstrate how to use @option{--extract} to extract a directory
file with an example.  Change to the @file{practice} directory if you
weren't there, and remove the files @file{folk} and @file{jazz}.  Then,
go back to the parent directory and extract the archive
@file{music.tar}.  You may either extract the entire archive, or you may
extract only the files you just deleted.  To extract the entire archive,
don't give any file names as arguments after the archive name
@file{music.tar}.  To extract only the files you deleted, use the
following command:

@smallexample
$ @kbd{tar -xvf music.tar practice/folk practice/jazz}
practice/folk
practice/jazz
@end smallexample

@noindent
If you were to specify two @option{--verbose} (@option{-v}) options, @command{tar}
would have displayed more detail about the extracted files, as shown
in the example below:

@smallexample
$ @kbd{tar -xvvf music.tar practice/folk practice/jazz}
-rw-r--r-- me user     28 1996-10-18 16:31 practice/jazz
-rw-r--r-- me user     20 1996-09-23 16:44 practice/folk
@end smallexample

@noindent
Because you created the directory with @file{practice} as part of the
file names of each of the files by archiving the @file{practice}
directory as @file{practice}, you must give @file{practice} as part
of the file names when you extract those files from the archive.

@node extracting untrusted archives
@subsection Extracting Archives from Untrusted Sources

Extracting files from archives can overwrite files that already exist.
If you receive an archive from an untrusted source, you should make a
new directory and extract into that directory, so that you don't have
to worry about the extraction overwriting one of your existing files.
For example, if @file{untrusted.tar} came from somewhere else on the
Internet, and you don't necessarily trust its contents, you can
extract it as follows:

@smallexample
$ @kbd{mkdir newdir}
$ @kbd{cd newdir}
$ @kbd{tar -xvf ../untrusted.tar}
@end smallexample

It is also a good practice to examine contents of the archive
before extracting it, using @option{--list} (@option{-t}) option, possibly combined
with @option{--verbose} (@option{-v}).

@node failing commands
@subsection Commands That Will Fail

Here are some sample commands you might try which will not work, and why
they won't work.

If you try to use this command,

@smallexample
$ @kbd{tar -xvf music.tar folk jazz}
@end smallexample

@noindent
you will get the following response:

@smallexample
tar: folk: Not found in archive
tar: jazz: Not found in archive
$
@end smallexample

@noindent
This is because these files were not originally @emph{in} the parent
directory @file{..}, where the archive is located; they were in the
@file{practice} directory, and their file names reflect this:

@smallexample
$ @kbd{tar -tvf music.tar}
practice/folk
practice/jazz
practice/rock
@end smallexample

@FIXME{make sure the above works when going through the examples in
order...}

@noindent
Likewise, if you try to use this command,

@smallexample
$ @kbd{tar -tvf music.tar folk jazz}
@end smallexample

@noindent
you would get a similar response.  Members with those names are not in the
archive.  You must use the correct member names, or wildcards, in order
to extract the files from the archive.

If you have forgotten the correct names of the files in the archive,
use @w{@kbd{tar --list --verbose}} to list them correctly.

@FIXME{more examples, here?  hag thinks it's a good idea.}

@node going further
@section Going Further Ahead in this Manual
@UNREVISED

@FIXME{need to write up a node here about the things that are going to
be in th