getopts

getopt -- short,long options

# Script is interested to take 
# - a flag
# - an option which takes a parameter
arg_list=$(getopt -o bp: --long boolean,param: -- "$@")
eval set -- "$arg_list"
while [ $# -gt 0 ] ; do
  case "$1" in
    -b | --boolean)
      echo "Parameter @ flag"
      shift
      ;;
    -p | --param)
      arg=${2}
      echo "Parameter @ parameter # ${arg}"
      shift 2
      ;;
    --)
      shift
      break
      ;;
  esac
done

getopts -- error checking

#!/bin/bash

# Script is interested to take 
# - a flag
# - an option which takes a parameter
arg_list="bp:"

echo "Number of arguments: $#"

# Parse passed parameters
while getopts ${arg_list} arg; do
  case ${arg} in
    b)
      echo "Parameter (${OPTIND}) @ flag"
      ;;
    p)
      param=${OPTARG}
      echo "Parameter (${OPTIND}) @ parameter # ${param}"
      ;;
    :)
      echo "Error! option # ${OPTARG} needs an argument"
      ;;
    *)
      echo "Error! unknown option # ${OPTARG}"
      ;;
  esac
done

# Output
# $ ./test2.sh 
# Number of arguments: 0
# $ ./test2.sh -b
# Number of arguments: 1
# Parameter (2) @ flag
# $ ./test2.sh -b -p test
# Number of arguments: 3
# Parameter (2) @ flag
# Parameter (4) @ parameter # test
# $ ./test2.sh -b -p
# Number of arguments: 2
# Parameter (2) @ flag
# ./test2.sh: option requires an argument -- p
# Error! unknown option # 
# $ ./test2.sh -b -q
# Number of arguments: 2
# Parameter (2) @ flag
# ./test2.sh: illegal option -- q
# Error! unknown option # 
# $ 

getopts -- silent error checking

#!/bin/bash

# Script is interested to take 
# - a flag
# - an option which takes a parameter
arg_list=":bp:"

echo "Number of arguments: $#"

# Parse each 
while getopts ${arg_list} arg; do
  case ${arg} in
    b)
      echo "Parameter (${OPTIND}) @ flag"
      ;;
    p)
      param=${OPTARG}
      echo "Parameter (${OPTIND}) @ parameter # ${param}"
      ;;
    :)
      echo "Error! option # ${OPTARG} needs an argument"
      ;;
    *)
      echo "Error! unknown option # ${OPTARG}"
      ;;
  esac
done

# Output
# $ ./test1.sh
# Number of arguments: 0
# $ ./test1.sh -b
# Number of arguments: 1
# Parameter (2) @ flag
# $ ./test1.sh -b -p test
# Number of arguments: 3
# Parameter (2) @ flag
# Parameter (4) @ parameter # test
# $ ./test1.sh -b -p
# Number of arguments: 2
# Parameter (2) @ flag
# Error! option # p needs an argument
# $ ./test1.sh -b -q
# Number of arguments: 2
# Parameter (2) @ flag
# Error! unknown option # q
# $