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

mattengland · 03-26-2006, 12:35 AM

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

Code:

#!/bin/sh
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 http://www.tldp.org/LDP/abs/html/x6659.html#JOBIDTABLE does not appear to function inside the script.

Code:

mengland@matts-laptop 12:33am [/data/tmp] 25> cat ks2.sh
#!/bin/sh
dd if=/dev/zero of=/dev/null &
sleep 1
kill %1
mengland@matts-laptop 12:33am [/data/tmp] 26> ./ks2.sh 
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:

Code:

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.

-Matt

gilead · 03-26-2006, 05:07 PM

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):

Code:

#!/bin/sh -x
dd if=/dev/zero of=/dev/null &
sleep 2
jobs
kill %1
sleep 2
jobs

And here is the output:

Code:

bash-3.1$ ./killer.sh 
+ dd if=/dev/zero of=/dev/null
+ sleep 2
+ jobs
[1]+  Running                 dd if=/dev/zero of=/dev/null &
+ kill %1
+ sleep 2
./killer.sh: line 6: 14766 Terminated              dd if=/dev/zero of=/dev/null
+ jobs
bash-3.1$