Shell: script that will start a process if it's not already running

start_if_not_running.ksh

#!/bin/ksh
###############################################################################
## Shell script that will start a process if it's not already running.
## Usage: start_if_not_running.ksh -n name
##        where "name" is the name of the process.  name must exist relative
##        to the current directory, or contain a full path.
###############################################################################

function Print
{
   print "`date +'%Y%m%d.%H%M%S'`: $*"
}

USAGE="Usage: `basename $0` -n name"
while getopts :n: args
do
   case $args in
      n)  NAME=$OPTARG;;
      :)  Print "Invalid command line: $USAGE"
          exit 1;;
      \?) Print "Invalid command line: $USAGE"
          exit 1;;
   esac
done

if [[ "$NAME" == "" ]]
then
   Print "$USAGE"
   exit 1
fi

function GetPID
{
   PID=`ps -ef | grep $NAME | grep -v grep | awk '{print $2}' | grep -v $$`
   echo "$PID"
}

##
## Get the PIDs of all $NAME processes.
##
PID=$(GetPID)
PID_COUNT=`echo $PID | wc -w`
if ((PID_COUNT == 0))
then
   Print "Starting $NAME"
   if [[ ! -f $NAME ]]
   then
      Print "ERROR: Cound not find '$NAME'"
      exit 2
   else
      nohup $NAME >$NAME.log 2>&1 &
      PID=$(GetPID)
      Print "PID is $PID"
   fi
elif ((PID_COUNT == 1))
then
   Print "$NAME already running as pid $PID"
else
   Print "WARNING: Found $PID_COUNT instances of $NAME"
fi