pid-file-daemon.sh

#!/bin/bash
# Uses a PID file to add daemon-like behavior to an arbitrary program.
################################################################################

# RHEL 6 doesn't include `realpath' in coreutils
function expandDir {
    set +x
    typeset DIR=$1
    if [[ ! -d $DIR ]]; then
        DIR=${1%/*}
        if [[ $DIR = $1 ]]; then
            DIR=.
        fi
    fi
    DIR=$(pushd $DIR > /dev/null ; dirs -l +0)
    echo ${DIR% *}
}

# RHEL 6 doesn't include `realpath' in coreutils
function realpath {
    declare SPATH="$1"
    declare RDIR=$(expandDir "$SPATH")
    declare BN="${SPATH##*/}"
    declare RPATH="${RDIR}"
    [[ "${RPATH##*/}" != "$BN" ]] && RPATH="${RPATH}/$BN"
    [[ -h "$RPATH" ]] && RPATH=$(readlink "$RPATH")
    echo "$RPATH"
}

function proc2cmd {
    declare PID=$1
    declare CMDLINE=$(echo $(cat /proc/$PID/cmdline | while read -r -d $'\0' LINE; do echo $LINE; done | tail -1))
    realpath "${CMDLINE}"
}

usage() {
  echo "Usage: `basename $0` PROGRAM {start|stop|restart|force-stop|force-restart|status} [PIDFILE|PID]" >&2
  echo "Where: PROGRAM is an executable file." >&2
  echo "       PIDFILE is the file that contains (or will contain) the PID." >&2
  echo "       PID is a process id to use in place of a PIDFILE." >&2
}

# At least two arguments are required.
if [[ -z "${1}" || -z "${2}" ]]; then
  usage
  exit 1
fi

# The first argument must be an actual file.
if [[ ! -e "${1}" ]]; then
  echo "File \"${1}\" not found. Exiting." 1>&2;
  exit 2
fi

PROGLONG=$(realpath "$1")
PROGSHORT=$(basename "${PROGLONG}")
PIDFILE=${PIDFILE:-"${PROGSHORT}.pid"}

# If there is a third argument, try to interpret it as a file or PID value.
if [[ ${3} ]]; then
  if [[ `expr $3 + 1 2> /dev/null` ]]; then
    PID=$3;
  elif [[ -e "${3}" || "${2}" == "start" ]]; then
    PIDFILE="${3}"
  else
    echo "Third argument must be a number or a file. (Found $3). Exiting." 1>&2;
    exit 3
  fi
fi

# Get the PID from PIDFILE if we don't have one yet.
if [[ -z "${PID}" && -e "${PIDFILE}" ]]; then
  PID=$(cat "${PIDFILE}");
fi

start() {
  echo "Starting $PROGSHORT (PID written to $PIDFILE)."
  "${PROGLONG}" & echo $! > "${PIDFILE}"
}

status() {
  if [[ -z "${PID}" ]]; then
    echo "${PROGSHORT} is not running (missing PID)."
  elif [[ -e /proc/${PID}/exe && "`proc2cmd ${PID}`" == $( realpath "${PROGLONG}" ) ]]; then
    echo "${PROGSHORT} is running (PID: ${PID})."
  else
    echo "${PROGSHORT} is not running (tested PID: ${PID})."
  fi
}

stop() {
  if [[ -z "${PID}" ]]; then
    echo "${PROGSHORT} is not running (missing PID)."
  elif [[ -e /proc/${PID}/exe && "`proc2cmd ${PID}`" == $( realpath "${PROGLONG}" ) ]]; then
    kill $1 ${PID}
    rm "${PIDFILE}"
  else
    echo "${PROGSHORT} is not running (tested PID: ${PID})."
  fi
}

case "$2" in
  start)
        start;
        ;;
  restart)
        stop; sleep 1; start;
        ;;
  stop)
        stop
        ;;
  force-stop)
        stop -9
        ;;
  force-restart)
        stop -9; sleep 1; start;
        ;;
  status)
        status
        ;;
  *)
        usage
        exit 4
        ;;
esac

exit 0

######################################################################
# This program is free software. It comes without any warranty, to
# the extent permitted by applicable law.
#
# If your jurisdiction supports the concept of Public Domain works,
# this program is released into the Public Domain.
#
# Otherwise this program is available under the following terms:
#---------------------------------------------------------------------
# Copyright (c) 2012, Rodney Waldhoff
# Modifications by Kel Byers, 2013
#
# Everyone is permitted to copy and distribute verbatim or modified
# copies of this program with or without this notice.
######################################################################