Scripting with 'for' and grep/egrep

Question

I'm trying to learn some more Linux, and from experience the best way is to try to bang your head against the wall. So now that I've done a task manually a few times I would like to automate it. This involves making a oneliner to kill some tasks so I can restart them.

At the moment I'm working with the following:

for i in `ps aux | egrep "[c]ouchpotato|[s]abnzbd|[s]ickbeard|[d]eluge|[n]zbhydra"|awk '{print $2, $11, $12}'`; do echo $i; done

The thing is that as soon as I run the for loop it breaks up the lines I get from awk.

Running ps aux | egrep "[c]ouchpotato|[s]abnzbd|[s]ickbeard|[d]eluge|[n]zbhydra"|awk '{print $2, $11, $12}' gives me the result I'm looking for, namely:

27491 /usr/local/couchpotatoserver-custom/env/bin/python /usr/local/couchpotatoserver-custom/var/CouchPotatoServer/CouchPotato.py
27504 /usr/local/deluge/env/bin/python /usr/local/deluge/env/bin/deluged
27525 /usr/local/deluge/env/bin/python /usr/local/deluge/env/bin/deluge-web
27637 /usr/local/nzbhydra/env/bin/python /usr/local/nzbhydra/share/nzbhydra/nzbhydra.py
27671 /usr/local/sabnzbd/env/bin/python /usr/local/sabnzbd/share/SABnzbd    /SABnzbd.py
28084 /usr/local/sickbeard-custom/env/bin/python /usr/local/sickbeard-custom/var/SickBeard/SickBeard.py

But adding it to my for loop breaks it into:

27491
/usr/local/couchpotatoserver-custom/env/bin/python
/usr/local/couchpotatoserver-custom/var/CouchPotatoServer/CouchPotato.py
27504
/usr/local/deluge/env/bin/python
/usr/local/deluge/env/bin/deluged
etc...

My goal is for $i to contain the whole line - is this possible? Also, is it possible to use get only the command from $11 and $12? I don't need to have the whole path to python and I don't even need to have the whole path to the application.

Thanks!

See Why does my shell script choke on whitespace or other special characters? - in particular the section Why do I need to write "$foo"? What happens without the quotes? — steeldriver, Jul 02 '17 at 14:43
@steeldriver: I'm not entirely sure what you wanted me to do here. I changed to bash, as I read from the article that it would accept spaces in a variable, I changed the backticks to $(...), but then all of a sudden there was just one long line. The for-loop would just hit everything in one go... — Lars, Jul 02 '17 at 16:33

score 1 · Accepted Answer · answered Jul 02 '17 at 17:13

Notice that the for loop output is broken apart at the word boundaries, viz., whitespaces/newlines. Whereas what you said you wanted is the whole line to come contained in the $i.

So you need to do these 2 things:

set the input field separator to a newline.

disable the wildcards expansion.

set -f;IFS=$'\n'; for i in `.....`;do echo "$i"; done

Note: DO NOT quote the backquotes else you shall end up giving to the for loop one big blob of argument,which would be the whole ps's output, and that doesn't do you no good.

HTH

Thanks! That fixed the main part of my problem :)
P.S. I wasn't allowed to upvote your answer as I'm too new... — Lars, Jul 02 '17 at 17:15

Scripting with 'for' and grep/egrep

1 Answers1