Control specific background subprocess in Bash script

Question

"Parent" Bash script

bash Child &
wait
sleep 5; echo "Main end" >>log.txt

"Child" script :

trap 'echo "Child end" >>log.txt;' ABRT
sleep 100
echo "Child end" >>log.txt

Run: bash Parent &

How to modify these scripts so that "kill -ABRT" would make Child exit with a trace in log.txt ? As is, Child ignores such signals. It does if the first line (trap) is removed, but then, no trace is left in log.txt upon "kill -ABRT".

Do you have control over your child scripts? Can you change their source? — Aleks-Daniel Jakimenko-A.
– Aleks-Daniel Jakimenko-A., Commented Sep 6, 2013 at 11:53
Yes, I'm writing an execution manager that builds a main script and launches it, having it, and its children (exec units, who launch each thousands of subprossesses) trace their start/stop/exit codes (final subprossesses too) to a couple of log files, so that a report can be built afterwards showing the user how much of each exec unit is started/finished{with succes, failed}, .. by parsing those log files. — ExpertNoob
– ExpertNoob, Commented Sep 6, 2013 at 12:35

Piotr Zierhoffer · Accepted Answer · 2013-09-06 11:54:22Z

1

I don't know if I get your question, but can't you operate on PID? You can get it/print it out from variable $!.

bash child1 &; echo $!;

And then just kill -ABRT that_pid.

Or do you want to kill a process running a specific child script?

answered Sep 6, 2013 at 11:54

Piotr Zierhoffer

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2 Comments

ExpertNoob Over a year ago

Yes, but how would child1 trap that signal ? If a trap is set in Main (so that it can trace its end too), child1 (with it's own trap) no longer gets that signal !! You can kill -ABRT pid_ch1 forever.. with no effect..

ExpertNoob Over a year ago

When a trap is set in Main, there is a strange "masking effect" that happens: it "closes children traps" who become unresponsive to signalling.. I couldn't get that under control.. I am actually asking if it's even possible to have separate control over Main/children.. Sending signals to Main (actually it's group process id) signals everybody which is not what I need.

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