CODEWITHSUNDEEP
linuxbashsleep
J.Doe
J.Doe

Reputation: 413

Linux: How to kill Sleep

More of a conceptual question. If I write a bash script that does something like

control_c()
{
echo goodbye
exit #$
}

trap control_c SIGINT

while true
do
sleep 10 #user wants to kill process here.
done

control+c won't exit when sleep 10 is running. Is it because linux sleep ignores SIGINT? Is there a way to circumvent this and have the user be able to cntrl+c out of a sleep?

Upvotes: 7

Views: 15943

Answers (3)

chepner
chepner

Reputation: 531165

What you are describing is consistent with the interrupt signal going to only your bash script, not the process group. Your script gets the signal, but sleep does not, so your trap cannot execute until after sleep completes. The standard trick is to run sleep in the background and wait on it, so that wait receives the interrupt signal. You should also then explicitly send SIGINT to any child processes still running, to ensure they exit.

control_c()
{
echo goodbye
kill -SIGINT $(jobs -p)
exit #$
}

trap control_c SIGINT

while true
do
sleep 10 &
wait
done

Upvotes: 13

Kal
Kal

Reputation: 411

control+c won't exit when sleep 10 is running.

That's not true. control+c DOES exit, even if sleep is running.

Are you sure your script is executing in bash? You should explicitly add "#!/bin/bash" on the first line.

Upvotes: 1

Azer H
Azer H

Reputation: 31

Since sleep is not bash function but external app, I guess Ctrl+C gets caught by sleep process, which normally should terminate it.
So for contorl_c function to be executed while in sleep, user must press Ctrl+C twice: 1st - to exit sleep, 2nd to get caught by bash trap.

Upvotes: 0

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