A template for setting up a daemon that can be interrupted nicely.

daemon.bash

#!/bin/bash
shopt -s -o nounset

##################################################
# Define Operating Variables
# DAEMON	Indicating whether to continue the loop or not
# SLEEP_TIME	Defines how long to sleep (in seconds) between executions
DAEMON=true
SLEEP_TIME=300

##################################################
# Trap SIGUSR2 to allow the daemon to cleanly exit.
# By issuing kill -SIGUSR2 <pid> OR pkill -SIGUSR2 daemon.bash
# we can allow the program to finish what it's doing instead
# of just stoping it.
trap "DAEMON=false" SIGUSR2

##################################################
# Run our daemon
while [ $DAEMON == "true" ]; do
	# Re-initialize the SLEEP_PID
	SLEEP_PID=""
	
	# This is the code that we want to periodically run
	<run>
	<code>
	<here>
	
	# Sleep
	sleep <time> &
	SLEEP_PID=$!
	
	# Trap SIGUSR1 to terminate the sleep early
	# Then wait for the sleep to end.
	# When one of these happens, the loop will continue
	trap "kill $SLEEP_PID" SIGUSR1
	wait $SLEEP_PID
	trap "" SIGUSR1
done