mydeamon.sh

#!/usr/bin/env sh
# ./mydeamon.sh TIMEOUT CHILDAPP
# 
# Creates a watchdog file WATCHDOG and executes CHILDAPP WATCHDOG.
# If CHILDAPP exits it is restarted.
# If CHILDAPP does not touch WATCHDOG within TIMEOUT seconds it is killed and restarted.
# This script stops CHILDAPP when it is aborted (Ctrl-C or SIGTERM).

set -e # abort this script if anything fails
SECONDS_UNTIL_KILL=$1
MYAPP=$2

if [ -z "$MYAPP" ] || [ -z "$SECONDS_UNTIL_KILL" ]; then
  echo "syntax: $0 timeout childapp"
  false
fi

WATCHDOG=`mktemp /tmp/mydeamon.XXXXXX`
REFFILE=`mktemp /tmp/mydeamon.XXXXXX`

# cleanup when this script finished
trap 'kill $MYAPP_PID; rm -f $WATCHDOG $REFFILE' EXIT

# loop to restart when dead
while true; do
  echo "$0: restarting $MYAPP $WATCHDOG"
  $MYAPP $WATCHDOG &
  MYAPP_PID=$!

  # loop to check age of $WATCHDOG, kill -0 dosn't kill, it just checks.
  while `kill -0 $MYAPP_PID`; do
    touch $REFFILE
    sleep $SECONDS_UNTIL_KILL

    if [ "$REFFILE" -nt "$WATCHDOG" ]; then
      echo "$0: $MYAPP didn't touch the watchdog. Sending SIGTERM."
      if ! kill "$MYAPP_PID"; then
        echo "$0: $MYAPP didn't respond to SIGTERM. Sending SIGKILL."
        kill -9 $MYAPP_PID
      fi
      break
    #else
    #  echo "$0: $MYAPP touched $WATCHDOG $LASTMOD seconds ago."
    fi
  done
done

mydeamontest.sh

#!/usr/bin/env bash
# A script used to test mydeamon.sh.
#
# Run: ./mydeamon.sh 5 ./mydeamontest.sh
# This script should be restarted.
#
# Run: ./mydeamon.sh 15 ./mydeamontest.sh
# This script should never be restarted and print a fail message.
#
# No dangling resources should be left when mydeamon.sh is aborted. These commans should be empty:
# ps -A | grep mydeamontest
# ls /tmp/mydeamon.*

WATCHDOG=$1
echo "$0: started $WATCHDOG"
sleep 1
touch $WATCHDOG
sleep 1
touch $WATCHDOG
sleep 1
touch $WATCHDOG
sleep 1
touch $WATCHDOG
sleep 1
touch $WATCHDOG
while true; do
	echo "$0: sleep 10"
	sleep 10
	touch $WATCHDOG
	echo "$0: failed, this script should have been killed"
done