bash_named_args.sh

#! /bin/bash

# See https://stackoverflow.com/questions/36495669/difference-between-terms-option-argument-and-parameter
# for the difference between:
# 1. Option
# 2. Parameter
# 3. Shell Parameter

# Test script to show how named arguments can be passed directly in a shell script.
# Uses a combination of while, case, and the the number of arguments defined in $#.

# List of required options.
last_name=
age=

# List of optional options.
first_name=
ethnicity=

# List of options with no parameters.
verbose=

# Basic processing with tolerance for equal signs or whitespace.
# Example: ./named_arg_processing_basic.sh -a 16 -l=Hill -f James --ethnicity=Caucasian
# Example 2: ./named_arg_processing_basic.sh -a 16 -l=Hill -f James -v --ethnicity=Caucasian
# Example 3: ./named_arg_processing_basic.sh -a 16 --invalid=this -l=Hill -f James -v --ethnicity=Caucasian -- 'Additional parameters' another parameter
while [ $# -gt 0 ]
do
  echo "Arg 1: $1"
  echo "Arg 2: $2"

  # For each argument, determine if:
  # 1. Argument is an option with a parameter
  # 2. If argument is an option with a parameter, parameter is separated with equal sign
  # 2. Argument is an option without a parameter

  if echo "$1" | grep -q '^-' && echo "$1" | grep -vq '=' && \
    (echo "$2" | grep -q '^-' || test -z "$2")
  # Argument is option without parameter or is last argument.
  then
    ARG_OPTION=$1
    ARG_PARAMETER=$1
    SHIFT_NUM=1
  elif echo "$1" | grep -q '^\-.*='
  # Argument is option with parameter, separated by equal sign.
  then
    ARG_OPTION=$(echo "$1" | grep -o '.*=' | grep -o '[^=]*')
    ARG_PARAMETER=$(echo "$1" | grep -o '[^=]*$')
    SHIFT_NUM=1
  else
  # Argument is option with parameter, not separated by equal sign.
    ARG_OPTION=$1
    ARG_PARAMETER=$2
    SHIFT_NUM=2
  fi

  echo "Val 1: $ARG_OPTION"
  echo "Val 2: $ARG_PARAMETER"

  case $ARG_OPTION in
    -l|--last_name)   last_name=$ARG_PARAMETER
                      ;;
    -a|--age)         age=$ARG_PARAMETER
                      ;;
    -f|--first_name)  first_name=$ARG_PARAMETER
                      ;;
    -v|--verbose)     verbose=true
                      ;;
    -e|--ethnicity)   ethnicity=$ARG_PARAMETER
                      ;;
    --)               shift
                      break
                      ;;
    -*|--*)           echo "unrecognized option: $ARG_OPTION" >&2
                      # Enable exit if you want to continue processing.
                      # exit 1
                      ;;
    *)                break
                      ;;
  esac
  
  # Add a newline.
  echo ""

  # Shift arguments forward.
  shift $SHIFT_NUM
done

# # Using Bash getopts function that comes with better features:
# # - Included error handling
# # - Indicates that an option takes an argument (prefix with :)
# # - Built-in support for -- to indicate that there are no more named arguments
# #
# # However, getopts has one HUGE downfall: It does not allow for optional parameters.
# # When an option requires a parameter, it needs to be required.
# # @see https://stackoverflow.com/questions/11517139/optional-option-argument-with-getopts for example.
# #
# # Example 1: ./named_arg_processing_basic.sh -a 16 -f Daniel -e=Caucasian
# # Example 2: ./named_arg_processing_basic.sh -a 16 -l=Hanold -f Daniel -e=Caucasian
# while getopts l:a:e:f: opt;
# do
#   echo "Option: $opt"
#   echo "Parameter: $OPTARG"
#   echo
#
#   CLEANED_ARG=$(echo $OPTARG | sed 's/^=//')
#   case "$opt" in
#     l)  last_name=$CLEANED_ARG
#         ;;
#     a)  age=$CLEANED_ARG
#         ;;
#     f)  first_name=$CLEANED_ARG
#         ;;
#     e)  ethnicity=$CLEANED_ARG
#         ;;
#   esac
# done
#
# # getops shifts options itself. Shifting after the loop will ensure that
# # "$@" only contains the non-option arguments to the script/function.
# shift $((OPTIND - 1))

echo "=== Debug Code ==="
echo "First Name is $first_name"
echo "Last Name is $last_name"
echo "Age is $age"
echo "Ethnicity is $ethnicity"
echo "Verbosity is $verbose"
echo "=== End Debug Code ==="
echo

# Print out variables.
if [ -n "$first_name" -a -n "$ethnicity" ];
then
  printf "Person %s %s is %s years of age. His ethnicity is %s.\n" $first_name $last_name $age $ethnicity
elif [ -n "$first_name" -a -z "$ethnicity" ];
then
  printf "Person %s %s is %s years of age.\n" $first_name $last_name $age
elif [ -z "$first_name" -a -n "$ethnicity" ];
then
  printf "Person %s is %s years of age. His ethnicity is %s.\n" $last_name $age $ethnicity
else
  printf "Person %s is %s years of age.\n" $last_name $age
fi