shell - Interrupt sleep in bash with a signal trap

Question

I'm trying to catch the SIGUSR1 signal in a bash script that is sleeping via the sleep command:

#!/bin/bash

trap 'echo "Caught SIGUSR1"' SIGUSR1

echo "Sleeping.  Pid=$$"
while :
do
    sleep 10
    echo "Sleep over"
done

The signal trap works, but the message being echoed is not displayed until the sleep 10 has finished.
It appears the bash signal handling waits until the current command finished before processing the signal.

Is there a way to have it interrupt the running sleep command as soon as it gets the signal, the same way a C program would interrupt the libc sleep() function?

Answer 1

#!/bin/bash

trap 'echo "Caught SIGUSR1"' SIGUSR1

echo "Sleeping.  Pid=$$"
while :
do
   sleep 10 &
   wait $!
   echo "Sleep over"
done