Sending the command(s) spawned by xargs to background

Question

I want to know how I can send the command(s) spawned by xargs to background. For example, consider

find . -type f  -mtime +7 | tee compressedP.list | xargs compress

I tried

find . -type f  -mtime +7 | tee compressedP.list | xargs -i{} compress {} &

.. and as unexpected, it seems to send xargs to the background instead?

How do I make each instance of the compress command go to the background?

Answer 1

You could probably make a very quick shellscript to call compress.

#!/bin/sh 
# call it 'compbg' and chmod a+x
compress $* &

then

find . -type f  -mtime +7 | tee compressedP.list | xargs -I{} compbg {}

Although I think you might be happier using this xargs argument:

 -P maxprocs
         Parallel mode: run at most maxprocs invocations of utility at once.

This command should find / tee / compress 10 files at a time until its done, as well as returning control immediately to the calling script/shell.

find . -type f  -mtime +7 | tee compressedP.list | xargs -I{} -P10 compress {} &

Answer 2

For SunOS you may have a look at GNU Parallel http://www.gnu.org/software/parallel/

find . -type f  -mtime +7 | tee compressedP.list | parallel compress

It has the added benefit of not crapping out if the filename contains ' " or space. Adding -j+0 will make it run one compress per CPU core.

Answer 3

This works for me when I want to edit all files that contain foo

grep -rl foo ./ | `xargs emacs` &