Shell Programming and Scripting

mailopt=FALSE
interval=5


while getopts mnf:t: option
do
case "$option"
in
m) mailopt=TRUE;;
t) interval=$OPTARG;;
f) if [ -f "$OPTARG" ]
then
echo "File exits"
else
echo "File doesnt exist"
fi
exit 1;;
\?) echo "Usage: mon [-m] [-t n] [-f] user"
    echo "      -m means to be informed by mail"
    echo "      -t means check every n secs"
    echo "  -f means check for existence fo a file"
    exit 1;;
esac
done

if [ "$OPTIND" -gt "$#" ]
then
echo "Missing user name!"
exit 2
fi

shiftcount=$((OPTIND - 1))
shift $shiftcount
user=$1

until who | grep "^$user " > /dev/null
do
sleep $interval
done

term=$(who | grep $user | cut -d' ' -f3)

if [ "$mailopt" = FALSE ]
then
echo "$user has logged on $user has logged on to terminal $term"
else
runner=$(who am i | cut -c1-7)
echo "$user has logged on to terminal $term" | mail $runner
fi

   while true
   do
        if [ -n "$FILE" ]
        then
             test -f "$FILE"
        else
            who | grep "^$user " > /dev/null
        fi
        [ $? -eq $INVERT ] && break
        sleep $interval
   done

##################################################################################
# Process options
#
#  add flags to this list
#  if the flag requires a parameter, follow it by a :
##################################################################################
[[ $VERBOSE -ge $TRUE ]] && print_status_message "STEP: Processing getopts..." STEP

while getopts ":f:hn#u:" OPT                            # While there is a command line option
do
   case $OPT in
      f)   fFLAG=$TRUE
           FILENAME=$OPTARG
           ;;

      h)   print_options
           ;;

      n)   nFLAG=$TRUE
           ;;

      u)   uFLAG=$TRUE
           USERNAME=$OPTARG
           ;;

      ?)   print_status_message "ERROR: Unknown flag encountered." ERROR
           print_options
           exit 2
           ;;

   esac
done                                            # end -

###################################################################################
# Main line here
###################################################################################
if [[ $fFLAG -eq $TRUE && $nFLAG -eq $FALSE ]]
then
   # check for filename
   if [[ -e $FILENAME ]]
   then
      print "Found $FILENAME."
      RETCODE=0

   else
      print "WARNING: $FILENAME was not found."
      RETCODE=-1

   fi

elif [[ $fFLAG -eq $TRUE && $nFLAG -eq $TRUE ]]
then
   # check NOT for filename
   if [[ ! -e $FILENAME ]]
   then
      print "$FILENAME was not found."
      RETCODE=0

   else
      print "WARNING: Found $FILENAME."
      RETCODE=-1

   fi

fi