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2.8.2 Extracting Specific Files

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

First, make sure you are in the ‘practice’ directory, and list the files in the directory. Now, delete the file, ‘blues’, and list the files in the directory again.

You can now extract the member ‘blues’ from the archive file ‘collection.tar’ like this:

 
$ tar --extract --file=collection.tar blues

If you list the files in the directory again, you will see that the file ‘blues’ has been restored, with its original permissions, data modification times, and owner.(1) (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 not have been made to the archive member.) The archive file, ‘collection.tar’, is the same as it was before you extracted ‘blues’. You can confirm this by running tar with ‘--list’ (‘-t’).

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

 
$ tar -x -f bfiles.tar --wildcards --no-anchored 'b*'

Here, ‘--wildcards’ instructs tar to treat command line arguments as globbing patterns and ‘--no-anchored’ informs it that the patterns apply to member names after any ‘/’ delimiter. The use of globbing patterns is discussed in detail in See section Wildcards Patterns and Matching.

You can extract a file to standard output by combining the above options with the ‘--to-stdout’ (‘-O’) option (see section Writing to Standard Output).

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


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