intermediate directories (GNU tar 1.34)

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### B.2 Restoring Intermediate Directories

A common concern is how to extract permissions and ownerships of intermediate directories when extracting only selected members from the archive. To illustrate this, consider the following archive:

    # tar tvf A.tar
    drwxr-xr-x root/root         0 2017-11-16 14:39 foo/
    dr-xr-x--- gray/user         0 2017-11-16 14:39 foo/bar/
    -rw-r--r-- gray/user        10 2017-11-16 14:40 foo/bar/file

Suppose you extract only the file `foo/bar/file`, while being ‘`root`’:

    # tar xvf A.tar foo/bar/file
    foo/bar/file

Now, let’s inspect the content of the created directories:

    # find foo -ls
    427257    0 drwxr-xr-x   3 root     root    16 Nov 17 16:10 foo
    427258    0 drwxr-xr-x   2 root     root    17 Nov 17 16:10 foo/bar
    427259    0 -rw-r--r--   1 gray     user    10 Nov  6 14:40 foo/bar/file

The requested file is restored, including its ownership and permissions. The intermediate directories, however, are created with the default permissions, current timestamp and owned by the current user. This is because by the time `tar` has reached the requested file, it had already skipped the entries for its parent directories, so it has no iformation about their ownership and modes.

To restore meta information about the intermediate directories, you’ll need to specify them explicitly in the command line and use the `--no-recursive` option (see recurse) to avoid extracting their content.

To automate this process, Neal P. Murphy proposed the following shell script31:

    #! /bin/sh
    (while read path
     do
       path=`dirname $path`
       while [ -n "$path" -a "$path" != "." ]
       do
         echo $path
         path=`dirname $path`
       done
     done < $2 | sort | uniq) |
     tar -x --no-recursion -v -f $1 -T - -T $2

The script takes two arguments: the name of the archive file, and the name of the file list file.

To complete our example, the file list will contain single line:

    foo/bar/file

Supposing its name is `file.list` and the script is named `restore.sh`, you can invoke it as follows:

    # sh restore.sh A.tar file.list

#### Footnotes

##### (31)

The original version of the script can be seen at http://lists.gnu.org/archive/html/bug-tar/2016-11/msg00024.html

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