Parallel processing of untar/remove in unix shell script - shell

Question

Question:
I want to untar a tarfile which has many tar files within itself and remove the files in all the tar files and I want all of these processes to run in parallel in Unix bash scripting.
Conditions:
The script should return an error if any untar/remove process has any error.
It should only return success after all N (untar and remove) processes complete successfully.
Proposed solution:
mkdir a
tar -C a -xvf b.tar
cd a
for i in *
do
rm -r $i &
done

Answer 1

If you have GNU Parallel http://www.gnu.org/software/parallel/ installed you can do this:
tar xvf foo.tgz | perl -ne 'print $l;$l=$_;END{print $l}' | parallel rm
It is useful if you do not have space to extract the full tar.gz file, but you need to process files as you unpack them:
tar xvf foo.tgz | perl -ne 'print $l;$l=$_;END{print $l}' | parallel do_stuff {}\; rm {}
You can install GNU Parallel simply by:
wget http://git.savannah.gnu.org/cgit/parallel.git/plain/src/parallel
chmod 755 parallel
cp parallel sem
Watch the intro videos for GNU Parallel to learn more:
https://www.youtube.com/playlist?list=PL284C9FF2488BC6D1

Answer 2

mkdir a
tar -C a -xvf b.tar
cd a
success=$(for i in *
do
rm -r $i || echo failed & # if a job fails false will be echoed
done
wait)
# if any of the jobs failed, success will be set to a value other than ""
[[ -z "$success" ]] && exit 0 || exit 1

Answer 3

The answer tar xvf a.tar | tac | xargs -P 4 rm -rv is inspired from Burton Samograd's comment about xargs -P
$ mkdir -p a/b/c/d
mkdir: created directory `a'
mkdir: created directory `a/b'
mkdir: created directory `a/b/c'
mkdir: created directory `a/b/c/d'
$ touch a/1 a/2 a/3 a/b/4 a/b/5
$ tar cf a.tar a
$ rm -rfv a
removed directory: `a/b/c/d'
removed directory: `a/b/c'
removed `a/b/4'
removed `a/b/5'
removed directory: `a/b'
removed `a/3'
removed `a/1'
removed `a/2'
removed directory: `a'
$ tar xvf a.tar | tac | xargs -P 4 rm -rv
removed `a/2'
removed `a/1'
removed `a/3'
removed `a/b/5'
removed `a/b/4'
removed directory: `a/b/c/d'
removed directory: `a/b/c'
removed directory: `a/b'
removed directory: `a'