Examples how to parse bash command line arguments

parse-bash-arguments

#!/bin/bash

# An example script how to parse a bash arguments with command
# link: https://stackoverflow.com/questions/192249/how-do-i-parse-command-line-arguments-in-bash

# Script version
SCRIPT_VERSION=0

# Help message
function usage() {
    cat <<EOF
Parse bash command line arguments.

Usage: $(basename $0) COMMAND [OPTIONS...] [ARGUMENTS...]

COMMANDS:
    example     Run the example command

EOF

}

# Parse command
COMMAND=$1
shift;

if [[ ! $COMMAND || $COMMAND = --help ]];then
    usage
    exit
fi

if [[ $COMMAND = --version ]]; then
    echo "$(basename $0) version: $SCRIPT_VERSION"
    exit
fi

# Parse options and arguments
SWITCH=0
ARGUMENTS=()
while [[ $# -gt 0 ]]
do
    key="$1"
    case $key in
        -s|--switch)
        SWITCH=1
        shift # past argument
        ;;    
        -i|--input)
        INPUT="$2"
        shift # past argument
        shift # past value
        ;;
        -i=*|--input=*)
        INPUT="${key#*=}"
        shift # past argument=value
        ;;
        *)    # unknown option
        ARGUMENTS+=("$1") # save it in an array for later
        shift # past argument
        ;;
    esac
done
set -- "${ARGUMENTS[@]}" # restore positional parameters

# Example command
if [[ $COMMAND = example ]]; then
    echo "COMMAND is \"${COMMAND}\""
    echo "INPUT is \"${INPUT}\""
    echo "SWITCH is ${SWITCH}. Default to 0"
    echo "Arguments is \"$@\""
    echo "Number of arguments: $#"
    exit
fi

# No command specified
if [[ $COMMAND ]]; then
    echo "Invalid command \"${COMMAND}\""
    echo
    usage
    exit 1
fi