Shell Programming and Scripting

#!/bin/bash
usage() {
  echo "$0: missing argument OR invalid option !
        Usage : $0 [-v][-h] -m|-r|-d
}

while getopts mrdvh opt; do
   case "$opt" in
      m)     monitor_flag=monitor;;
      r)     report_flag=report;;
      d)     delete_flag=delete;;
      v)     verbose=True;;
      h)     usage
             exit 0;;
     [?])   usage
   esac
done


if [ "$monitor_flag" = "monitor" -o "$delete_flag" = "delete" -o "$report_flag" = "report" ]; then
   echo "correct usage"
else
   echo "Usage:"
   usage
   exit 1;
fi
....
..

#!/bin/bash


usage() {
  (( h )) || 
    printf >&2 '%s: missing argument OR invalid option!\n' "${0##*/}"
  printf >&2 'Usage : %s [-v][-h] -m|-r|-d\n' "${0##*/}"
  }

(( $# )) || usage 

while getopts :mrdvh opt; do
   case $opt in

     ( h )     
        h=1 
        usage 
        exit 0   
        ;;

     ( v )     
        verbose=True 
        ;;

     ( m )     
        monitor_flag=monitor 
        (( ++c ))
        ;;

     ( r )     
        report_flag=report   
        (( ++c ))
        ;;
      
     ( d )     
        delete_flag=delete
        (( ++c ))
        ;;

     ( ? )   
      usage
   esac
done

(( c > 1 )) &&
  usage