An example of how to use bash getopts

getopts.sh

#!/bin/bash

######################################################################
#This is an example of using getopts in Bash. It also contains some
#other bits of code I find useful.
#Author: Linerd
#Website: http://tuxtweaks.com/
#Copyright 2014
#License: Creative Commons Attribution-ShareAlike 4.0
#http://creativecommons.org/licenses/by-sa/4.0/legalcode
######################################################################

#Set Script Name variable
SCRIPT=`basename ${BASH_SOURCE[0]}`

#Initialize variables to default values.
OPT_A=A
OPT_B=B
OPT_C=C
OPT_D=D

#Set fonts for Help.
NORM=`tput sgr0`
BOLD=`tput bold`
REV=`tput smso`

#Help function
function HELP {
  echo -e \\n"Help documentation for ${BOLD}${SCRIPT}.${NORM}"\\n
  echo -e "${REV}Basic usage:${NORM} ${BOLD}$SCRIPT file.ext${NORM}"\\n
  echo "Command line switches are optional. The following switches are recognized."
  echo "${REV}-a${NORM}  --Sets the value for option ${BOLD}a${NORM}. Default is ${BOLD}A${NORM}."
  echo "${REV}-b${NORM}  --Sets the value for option ${BOLD}b${NORM}. Default is ${BOLD}B${NORM}."
  echo "${REV}-c${NORM}  --Sets the value for option ${BOLD}c${NORM}. Default is ${BOLD}C${NORM}."
  echo "${REV}-d${NORM}  --Sets the value for option ${BOLD}d${NORM}. Default is ${BOLD}D${NORM}."
  echo -e "${REV}-h${NORM}  --Displays this help message. No further functions are performed."\\n
  echo -e "Example: ${BOLD}$SCRIPT -a foo -b man -c chu -d bar file.ext${NORM}"\\n
  exit 1
}

#Check the number of arguments. If none are passed, print help and exit.
NUMARGS=$#
echo -e \\n"Number of arguments: $NUMARGS"
if [ $NUMARGS -eq 0 ]; then
  HELP
fi

### Start getopts code ###

#Parse command line flags
#If an option should be followed by an argument, it should be followed by a ":".
#Notice there is no ":" after "h". The leading ":" suppresses error messages from
#getopts. This is required to get my unrecognized option code to work.

while getopts :a:b:c:d:h FLAG; do
  case $FLAG in
    a)  #set option "a"
      OPT_A=$OPTARG
      echo "-a used: $OPTARG"
      echo "OPT_A = $OPT_A"
      ;;
    b)  #set option "b"
      OPT_B=$OPTARG
      echo "-b used: $OPTARG"
      echo "OPT_B = $OPT_B"
      ;;
    c)  #set option "c"
      OPT_C=$OPTARG
      echo "-c used: $OPTARG"
      echo "OPT_C = $OPT_C"
      ;;
    d)  #set option "d"
      OPT_D=$OPTARG
      echo "-d used: $OPTARG"
      echo "OPT_D = $OPT_D"
      ;;
    h)  #show help
      HELP
      ;;
    \?) #unrecognized option - show help
      echo -e \\n"Option -${BOLD}$OPTARG${NORM} not allowed."
      HELP
      #If you just want to display a simple error message instead of the full
      #help, remove the 2 lines above and uncomment the 2 lines below.
      #echo -e "Use ${BOLD}$SCRIPT -h${NORM} to see the help documentation."\\n
      #exit 2
      ;;
  esac
done

shift $((OPTIND-1))  #This tells getopts to move on to the next argument.

### End getopts code ###


### Main loop to process files ###

#This is where your main file processing will take place. This example is just
#printing the files and extensions to the terminal. You should place any other
#file processing tasks within the while-do loop.

while [ $# -ne 0 ]; do
  FILE=$1
  TEMPFILE=`basename $FILE`
  #TEMPFILE="${FILE##*/}"  #This is another way to get the base file name.
  FILE_BASE=`echo "${TEMPFILE%.*}"`  #file without extension
  FILE_EXT="${TEMPFILE##*.}"  #file extension


  echo -e \\n"Input file is: $FILE"
  echo "File withouth extension is: $FILE_BASE"
  echo -e "File extension is: $FILE_EXT"\\n
  shift  #Move on to next input file.
done

### End main loop ###

exit 0