Extract single file from tar to other folder

aixdirectoryscriptingtar

I've searched for multiple forums for this questions and have seen different answers but so far, nothing have worked yet even from the ones I've seen here.

I want to extract a single file from a tar to a different directory.

I've tried this:

tar xvf file.tar -C /home/dir/ filename

or this:

tar -x filename -f file.tar -C /home/dir

But got these errors respectively:

x filename, 14826 bytes, 29 media blocks.
File -C not present in the archive.
File /home/dir not present in the archive.

and:

tar: /dev/rmt0: A file or directory in the path name does not exist.

The first extracted the file but in the same directory, not to the folder I wanted.

Best Answer

In most versions of tar, there are two different modes, depending on whether you put a minus before your options.

The top of the AIX tar man page summarizes the differences:

Berkeley Standards:

tar {c|r|t|u|x} ... [ Archive ] Directory | File ...

X/Open Standards:

tar {-c|-r|-t|-u|-x} ... [-f Archive] ... [-C Directory] File | Directory...

Without the minus, tar works in Berkeley compatibility mode. In this mode, the options don't follow now-standard UNIX command line conventions. Instead, all the flags must be placed together (in any order). The f flag means that the first word after the flags is a file name that should be used instead of the tape drive, /dev/rmt0. (The t in tar stands for tape, and the defaults reflect this.) Also note that there is no -C option in compatibility mode.

With the minus, tar works like most UNIX commands. All the flags (and their arguments) must be specified first, then the non-flags come after. -f takes a file name as an argument (essentially, the file name belongs to the -f flag), so the file.tar must come immediately after the -f. That's why the man page says [-f Archive] with Archive next to the -f. But -x takes no arguments (filename does not belong to the -x). Again, looking at the man page, filename in your example corresponds to File | Directory..., which are all the way at the end of the command line.

The fixed versions of your commands look like

(cd /home/dir; tar xvf /path/to/file.tar filename)

and

tar -x -f file.tar -C /home/dir filename

GNU tar does something similar. The Three Option Styles does a good job of explaining the differences.

Related Solutions

How to extract a single file from tbz

tar -xvjf itunes20140618.tbz itunes20140618/video

That should do it for this case, but if you need more help do:

info tar

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. (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).

How to securely extract an untrusted tar file

You don't need the paranoia at all. GNU tar — and in fact any well-written tar program produced in the past 30 years or so — will refuse to extract files in the tarball that begin with a slash or that contain .. elements, by default.

You have to go out of your way to force modern tar programs to extract such potentially-malicious tarballs: both GNU and BSD tar need the -P option to make them disable this protection. See the section Absolute File Names in the GNU tar manual.

The -P flag isn't specified by POSIX,¹ though, so other tar programs may have different ways of coping with this. For example, the Schily Tools' star program uses -/ and -.. to disable these protections.

The only thing you might consider adding to a naïve tar command is a -C flag to force it to extract things in a safe temporary directory, so you don't have to cd there first.

Asides:

Technically, tar isn't specified by POSIX any more at all. They tried to tell the Unix computing world that we should be using pax now instead of tar and cpio, but the computing world largely ignored them.

It's relevant here to note that the POSIX specification for pax doesn't say how it should handle leading slashes or embedded .. elements. There's a nonstandard --insecure flag for BSD pax to suppress protections against embedded .. path elements, but there is apparently no default protection against leading slashes; the BSD pax man page indirectly recommends writing -s substitution rules to deal with the absolute path risk.

That's the sort of thing that happens when a de facto standard remains in active use while the de jure standard is largely ignored.

Best Answer

Related Solutions

How to extract a single file from tbz

How to securely extract an untrusted tar file

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