Daemonized bash script

daemon.sh

#!/bin/bash
set -e

PIDFILE="daemon.pid"
LOCKFILE="daemon.lock"
LOGFILE="daemon.log"
SELF=$0
ACTION=$1
ARGS="$*"

function _help() {
    echo "Usage: $SELF (run|start|status|stop|help)"
    echo ""
    echo "  run     run the program"
    echo "  start   run the program as daemon"
    echo "  status  status of the running program"
    echo "  stop    stop the running program"
    echo "  help    display this message"
}

function _clean() {
    echo "Cleaning $LOCKFILE" >> $LOGFILE
    rm -f $LOCKFILE $PIDFILE
    exit
}

function _exit() {
    echo "Exited" >> $LOGFILE
    _clean
}

function _sigterm() {
    echo "Recived SIGTERM" >> $LOGFILE
    _clean
}

function _sigkill() {
    echo "Recived SIGKILL" >> $LOGFILE
    _clean
}

function _run() {
    (flock -e -n 9 || exit 1
        trap _exit EXIT
        trap _sigterm SIGTERM
        trap _sigkill SIGKILL

        echo $BASHPID >> $PIDFILE

        _main
    ) 9> $LOCKFILE
}

function _is_started() {
    [ ! -e "$PIDFILE" ] && return 1
    ps -Ao pid | grep "$(cat $PIDFILE)" > /dev/null
    return $?
}

function _status() {
    if _is_started; then
        echo "Started"
    else
        echo "Stoped"
    fi
}

function _start() {
    if _is_started; then
        echo "Already started"
        return
    fi

    nohup $SELF run &>> $LOGFILE &
    sleep 1
    _status
}

function _stop() {
    if ! _is_started; then
        echo "Not started"
        return
    fi

    kill $(cat $PIDFILE)
    sleep 1
    _status
}

function _main() {
    while true; do
        echo "ping $(date +%F_%T)"
        sleep 1
    done
}

case $ACTION in
    run )
        _run
        ;;
    start )
        _start
        ;;
    stop )
        _stop
        ;;
    status )
        _status
        ;;
    *)
        _help
        ;;
esac