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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 section Descending into Directories) to avoid extracting their content.
To automate this process, Neal P. Murphy proposed the following shell script(31):
#! /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:
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
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