trap

[atagtm]

In dmenu_timer, the trap is in the wrong place, in my opinion. You should put it before the loop ✌️
Like this:

timer () {
trap cleanup SIGHUP SIGINT SIGQUIT SIGABRT SIGTREM #1 2 3 6 15
while [ $TOTAL_SECONDS -gt 0 ]; do
    MIN=$(printf "%02d" $((TOTAL_SECONDS / 60)))
    SEC=$(printf "%02d" $((TOTAL_SECONDS % 60)))
    echo "  $MIN $SEC " > /tmp/timericon;
    pkill -RTMIN+3 dwmblocks;
    sleep 1
    ((TOTAL_SECONDS--))
done


echo "" > /tmp/timericon;
pkill -RTMIN+3 dwmblocks;
notify-send "Timer ended, take a break"
}

I'd put the ending into the cleanup function (followed by an 'exit', and just call it (even if a signal arrives, or the loop ends)... as long as you don't care about correct exit codes :D

Absolute overkill version:

cleanup() {
echo "" > /tmp/timericon;
pkill -RTMIN+3 dwmblocks;
notify-send "Timer ended, take a break"

case $1 in
    "SIGHUP") EXIT_CODE=1 ;;     # Custom exit code for SIGHUP
    "SIGINT") EXIT_CODE=130 ;;   # 128 + 2
    "SIGQUIT") EXIT_CODE=131 ;;  # 128 + 3
    "SIGABRT") EXIT_CODE=134 ;;  # 128 + 6
    "SIGTERM") EXIT_CODE=143 ;;  # 128 + 15
    *) EXIT_CODE=0 ;;            # Default exit code
esac
exit $EXIT_CODE
}

timer () {
trap 'cleanup "SIGHUP"' SIGHUP 
trap 'cleanup "SIGINT"' SIGINT 
trap 'cleanup "SIGQUIT"' SIGQUIT 
trap 'cleanup "SIGABRT"' SIGABRT 
trap 'cleanup "SIGTERM"' SIGTERM
while [ $TOTAL_SECONDS -gt 0 ]; do
    MIN=$(printf "%02d" $((TOTAL_SECONDS / 60)))
    SEC=$(printf "%02d" $((TOTAL_SECONDS % 60)))
    echo "  $MIN $SEC " > /tmp/timericon;
    pkill -RTMIN+3 dwmblocks;
    sleep 1
    ((TOTAL_SECONDS--))
done

cleanup
}

Bonus idea, you can save the PID like 'echo "$$" > /tmp/timerpid', then you can stop the timer anytime with 'kill -HUP $(cat /tmp/timerpid). Of course you should 'rm' this file in cleanup()
3.7.5 Exit Status
trap(1p)

[BreadOnPenguins]

Great suggestion, and thanks to it I now have a better understanding of trap and exit codes.

Ended up with this,

cleanup() {
echo "" > /tmp/timericon;
pkill -RTMIN+3 dwmblocks;
exit 0
}

timer () {
trap cleanup SIGHUP SIGINT SIGQUIT SIGABRT SIGTERM # 1 2 3 6 15
while [ $TOTAL_SECONDS -gt 0 ]; do
    MIN=$(printf "%02d" $((TOTAL_SECONDS / 60)))
    SEC=$(printf "%02d" $((TOTAL_SECONDS % 60)))
    echo "  $MIN $SEC " > /tmp/timericon;
    pkill -RTMIN+3 dwmblocks;
    sleep 1
    ((TOTAL_SECONDS--))
done

notify-send "Timer ended, take a break"
cleanup
}

Much appreciated!