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Old 03-26-2006, 12:35 AM   #1
Registered: Nov 2004
Location: Chicago, IL USA
Posts: 42

Rep: Reputation: 15
bash script: run multiple jobs in bg, & kill them separately?

The following code kills off a backgrounded process in a bash shell after 4 seconds:

dd if=/dev/zero of=/dev/null &
sleep 4
kill $!
I also want to write additional scripts that background many processes at the same time, and selectively kill different backgrounded processes/jobs selectively (based on some arbitrary criteria that I make in my script).

How can I do this?

The 'kill %N' construct as per does not appear to function inside the script.

mengland@matts-laptop 12:33am [/data/tmp] 25> cat
dd if=/dev/zero of=/dev/null &
sleep 1
kill %1
mengland@matts-laptop 12:33am [/data/tmp] 26> ./ 
kill: illegal pid: %1
mengland@matts-laptop 12:33am [/data/tmp] 27> ps -ef | grep dd
mengland    3316       1   0  00:33:35 /usr/bin/dd
mengland@matts-laptop 12:33am [/data/tmp] 28> killall dd
mengland@matts-laptop 12:33am [/data/tmp] 29> !ps
ps -ef | grep dd
mengland@matts-laptop 12:33am [/data/tmp] 30>
Notice the:

kill: illegal pid: %1
Why does that not work? If it could, I could (seemingly) selectively kill processes I put in background via the bash script.

Any thoughts?

fyi, the same thing happens for a plain 'kill %' in the script.

Old 03-26-2006, 05:07 PM   #2
Senior Member
Registered: Dec 2005
Location: Brisbane, Australia
Distribution: Slackware64 14.0
Posts: 4,125

Rep: Reputation: 165Reputation: 165
Is /bin/sh linked to /bin/bash on your system? Your syntax is correct for bash - if you search man bash for job control, it describes the behaviour you're looking for. It runs properly on my system - here is the script (the -x is for debug output):
#!/bin/sh -x
dd if=/dev/zero of=/dev/null &
sleep 2
kill %1
sleep 2
And here is the output:
bash-3.1$ ./ 
+ dd if=/dev/zero of=/dev/null
+ sleep 2
+ jobs
[1]+  Running                 dd if=/dev/zero of=/dev/null &
+ kill %1
+ sleep 2
./ line 6: 14766 Terminated              dd if=/dev/zero of=/dev/null
+ jobs


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