#!/bin/bash
# chkconfig: 35 20 80
# description: My little daemon manager
# processname: mylittledaemon

# =============================================================================
DAEMON_COPYRIGHT="Copyright (c) 2010 by Etretat Logiciels, LLC. All rights reserved."
  DAEMON_VERSION=1.0.0
#
#
NAME=mylittledaemon
#          Start/stop/restart/etc. for my little daemon daemon.
#
#          During my little daemon manager installation, the following command
#          is issued:
#          chkconfig --levels 35 mylittledaemon on
#
#          Ordinarily, the license and log files are these and aren't changed.
#          Whatever the case, $DAEMON_HOME must be set and accurate before this
#          script is executed.
LICENSE_FILE=/opt/$DAEMON_HOME/licenses/daemon_ts.lic
LOGFILE_PATH=/var/log/$DAEMON_HOME/mylittledaemon.log
#
#          These are the possible options, ordinarily never passed, to this
#          script. These are pretty much the only, possible options.
OPTIONS="-c $LICENSE_FILE -l $LOGFILE_PATH"
#
#          Platform support
#          Deal with what platform we're running on: we claim to support Red
#          Hat Enterprise Linux and SuSE Linux Enterprise Server. We'll be
#          doing Solaris later, but there will be no sign of that in here since
#          the daemon init script is a purely Linux phenomenon.
if [ -f "/etc/rc.d/init.d/functions" ]; then
  PLATFORM="RHEL"
  . /etc/rc.d/init.d/functions
elif [ -f /etc/rc.status ] ; then
  PLATFORM="SLES"
  . /etc/rc.status
else
  echo "Platform is unsupported."
  exit 0
fi
#
#          (Note: this document is entabbed at 2.)
# =============================================================================
          TRUE=1
         FALSE=0
   EXIT_STATUS=0
daemon_running=$FALSE

DoUsage()
{
  echo "Usage: /etc/init.d/mylittledaemon [-c] [-l] {start|stop|restart|status}"
  echo
  echo "Options"
  echo "  -c license-file-path New path to license file. Default is"
  echo "      $LICENSE_FILE"
  echo "  -l logfile-path      New location of log file. Default is"
  echo "      $LOGFILE_PATH"
  echo
  echo "Note: it is unusual to provide any command-line options."
  echo "See also manpage for mylittledaemon."
  echo
  DoVersion
}

DoVersion()
{
  echo "mylittledaemon: version $DAEMON_VERSION"
  echo $DAEMON_COPYRIGHT
}

SeeIfDaemonIsRunning()
{
  # Determine whether the daemon already happens to be running since it's
  # important depending on what operation this script is to undertake. Note:
  # we don't have to test this ps command because we know both Red Hat and SuSE
  # support it. If other Linux platform support is added, we might have to use
  # a different one and parse it differently too.
  PS_CMD="ps -e -o pid,args"

  # Get the list of processes whose status contains "mylittledaemon" and filter
  # out the ones due to grep, [g]vi[m], this script executing, etc. (mostly
  # happening during initial bring up and testing) because they don't count as
  # instances of this daemon running.
  #                    find daemon  no greps       no sh -x     no editing
  proc_list=`$PS_CMD | grep $NAME | grep -v grep | grep -v sh | grep -v vi`

  # Some presumably real instances to sort through (almost certainly never more
  # than one single process). Here's the business end of this function:
  # producing a process id or a list of process ids.
   procs=`echo $proc_list | awk '{print $1}'`

  # If we're left with anything, then it means the daemon is running!
  if [ -n "$procs" ]; then
    daemon_running=$TRUE
  else
    daemon_running=$FALSE
  fi
}

start()
{
  echo -n "Starting $NAME: "

  case "$PLATFORM" in
    "RHEL")
      daemon ./$NAME $OPTIONS
      EXIT_STATUS=$?
      ;;
    "SLES")
      /sbin/startproc ./$NAME $OPTIONS
      rc_status -v
      ;;
  esac

  echo
  [ $EXIT_STATUS -eq 0 ] && touch /var/lock/subsys/$NAME;
}

stop()
{
  echo -n "Stopping $NAME: "

  case "$PLATFORM" in
    "RHEL")       killproc $NAME ;;
    "SLES") /sbin/killproc $NAME ;;
  esac

  EXIT_STATUS=$?
  # at very least, Red Hat wants lock file removed, so we'll do it for all
  rm -f /var/lock/subsys/$NAME
  echo

  if [ "$PLATFORM" = "SLES" ]; then
    rc_status -v
  fi
}

getstatus()
{
  echo -n "Checking $NAME: "

  case "$PLATFORM" in
    "RHEL")
      status $NAME
      EXIT_STATUS=$?
      ;;
    "SLES")
      /sbin/checkproc ./$NAME
      rc_status -v
      EXIT_STATUS=$?
      ;;
  esac
}

# -----------------------------------------------------------------------------
# Script entry point...
# -----------------------------------------------------------------------------
# Switch to the daemon's home directory to do all of this...
cd /opt/$DAEMON_HOME/sbin

if [ $? -ne 0 ]; then
  echo "Unable to find $NAME's directory."
  exit 1
fi

# Ensure the daemon exists...
if [ ! -x "$NAME" ]; then
  echo "$NAME could not be found."
  exit 1
fi

# Enforce that only root can do this...
if [ "`id | sed 's/uid=\([0-9]*\).*/\1/'`" -ne 0 ] ; then
  echo "This script can only be run by root."
  exit
fi

# Cover the modern options: either way, we don't continue on. We assume a
# minimal level of competence here: we're not idiot-proofing this script. If
# they want help or the version, it will be the first and probably only thing
# passed.
arg=$1
if [ "$arg" = "--help" ]; then
  DoUsage
  exit 0
elif [ "$arg" = "--version" ]; then
  DoVersion
  exit 0
fi

# Parse command-line arguments if any. There would not usually be any. Skip
# gracefully over any invalid arguments if not too goopy.
while getopts "hc:l:v" opt; do
  case $opt in
    h) DoUsage    ; exit 0                          ;;
    v) DoVersion  ; exit 0                          ;;
    c) shift      ; LICENSE_FILE=$1 ; shift         ;;
    l) shift      ; LOGFILE_PATH=$1 ; shift         ;;
    *) echo "WARNING: Ignoring invalid option ($1)" ;;
  esac
done

operation=$1
EXIT_STATUS=0

# Determine what platform (OS) is underneath us and check to see if the daemon
# is already running.
SeeIfDaemonIsRunning

# Here's what we really came to do...
case "$operation" in
  start)    # -----------------------------------------------------------------
    if [ $daemon_running -eq $FALSE ]; then
      start
    else
      echo "$NAME appears already to be running."
      if [ "$PLATFORM" = "SLES" ]; then
        rc_status -s
      fi
    fi
    ;;

  stop)     # -----------------------------------------------------------------
    if [ $daemon_running -eq $TRUE ]; then
      stop
    else
      echo "$NAME does not appear to be running."
      if [ "$PLATFORM" = "SLES" ]; then
        rc_status -s
      fi
    fi
    ;;

  restart)  # -----------------------------------------------------------------
    if [ $daemon_running -eq $TRUE ]; then
      stop
      sleep 1
    fi
    start
    EXIT_STATUS=$?
    ;;

  status)   # -----------------------------------------------------------------
    getstatus
    ;;

  *)        # -----------------------------------------------------------------
    echo "Usage: $NAME {start|stop|restart|status}"
    exit 1
esac

case "$PLATFORM" in
  "RHEL") exit $EXIT_STATUS ;;
  "SLES") rc_exit           ;;
esac
# vim: set tabstop=2 shiftwidth=2 noexpandtab:

Copyright ©2010 by Russell Bateman and Etretat Logiciels, LLC.

Permission is granted for any derivational use. You are forbidden only from reposting the texts and any sources of this article without express permission of the author.