Find extracted directory name from tar file

Question

I have a project where I am downloading and compiling a bunch of files. The assumptions I can make about this files are:

• there will only be one top level directory
• the folder name doesn't necessarily match the tar.xz/gz filename (in other words something-1.3.5a.tar.gz might extract to a folder called something-1.3.5)

In order to lessen the amount of typing I have to do I wrote a small script, which among other things does the follow:

• extracts the tar.xz/gz file
• cds into the directory

My current hack is to do something like this:

test1=$(tar -axvf something-1.3.5a.tar.gz)

cd $(echo $test1 | cut -f1 -d" ")

Basically what this does is it captures the output of the extraction, and takes the first line (which is the top level directory) and then cds into it.

So, my question is this, is there a cleaner/better way of doing this?

Answer 1

#!/bin/sh
Dir_name=`tar -tzf something-1.3.5a.tar.gz | head -1 | cut -f1 -d"/"`
echo $Dir_name

tar options details,
-t, --list 
-z, --gzip, --ungzip               filter the archive through gzip
-f, --force-local              archive file is local even if has a colon

Here, we are getting the list of file in tar and taking the first line using head -1 cmd, extracting the first field using cut cmd.

Answer 2

If you have one top directory and nothing, you can simply remember what directories there are before you run tar, and see what you have after you do that, assuming nobody else have changed that directory.

 # ksh terminology: set -A BEFORE .*/ */
 BEFORE=(.*/ */)
 tar -xf blah blah blah
 AFTER=(.*/ */)
 # We can make it O(n), since glob outputs can be assumed to be sorted.
 # Do it.
 for (( i = 0; i < "${#BEFORE[@]}"; i++ )); do
    [ "${BEFORE[i]}" == "${AFTER[i]}" ] || break
 done
 cd "${AFTER[i]}"

This should work with all shells that has arithmetic for, arrays starting with a zero index and with ${#arr[@]} to access array member count.

There is actually one problem, since */ may expand into literally */ where there is no match. In bash (assuming you are using bash because of your tag), you can set shopt -s nullglob for that.

Using */ restricts the globbed items to directories, so you won't worry about files -- Extra files still make it only one dir :)

Answer 3

With a tar.bz2 file, to not get something like:

0               0 2019-04-02 17:20 folder name

I'm using -tf options:

tar -tf file_name.tar.bz2 | head -1 | cut -f1 -d"/"