Shell – How to Extract a Single Folder from a Large tar.gz Archive

gzipshelltar

I am using this command on a 5GB archive

tar -zxvf archive.tar.gz /folder/in/archive

is this the correct way to do this? It seems to be taking forever with no command line output…

Best Answer

tar stores relative paths by default. GNU tar even says so if you try to store an absolute path:

tar -cf foo.tar /home/foo
tar: Removing leading `/' from member names

If you need to extract a particular folder, have a look at what's in the tar file:

tar -tvf foo.tar

And note the exact filename. In the case of my foo.tar file, I could extract /home/foo/bar by saying:

tar -xvf foo.tar home/foo/bar # Note: no leading slash

So no, the way you posted isn't (necessarily) the correct way to do it. You have to leave out the leading slash. If you want to simulate absolute paths, do cd / first and make sure you're the superuser. Also, this does the same:

tar -C / -xvf foo.tar home/foo/bar # -C is the ‘change directory’ option

There are very obvious, good reasons why tar converts paths to relative ones. One is the ability to restore an archive in places other than its original source. The other is security. You could extract an archive, expect its files to appear in your current working directory, and instead overwrite system files (or your own work) elsewhere by mistake.

Note: if you use the -P option, tar will archive absolute paths. So it always pays to check the contents of big archives before extracting.

Related Solutions

Tar Gzip – How to Efficiently Remove Files from Large .tgz

With GNU tar, you can do:

pigz -d < file.tgz |
  tar --delete --wildcards -f - '*/prefix*.jpg' |
  pigz > newfile.tgz

With bsdtar:

pigz -d < file.tgz |
  bsdtar -cf - --exclude='*/prefix*.jpg' @- |
  pigz > newfile.tgz

(pigz being the multi-threaded version of gzip).

You could overwrite the file over itself like:

{ pigz -d < file.tgz |
    tar --delete --wildcards -f - '*/prefix*.jpg' |
    pigz &&
    perl -e 'truncate STDOUT, tell STDOUT'
} 1<> file.tgz

But that's quite risky, especially if the result ends up being less compressed than the original file (in which case, the second pigz may end up overwriting areas of the file which the first one has not read yet).

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).

Best Answer

Related Solutions

Tar Gzip – How to Efficiently Remove Files from Large .tgz

How to extract a single file from tbz

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