optargs

Command line option processing in Bash can be done using various methods such as getopt and getopts. Here, we explore different techniques along with examples to handle command line arguments efficiently.

Basic Syntax

./script.sh [options] [arguments]

Processing Options

Method 1: Using getopts with Short Options

while getopts ":ab:c" option; do
    case $option in
        a)
            # Option 'a' is present
            ;;
        b)
            # Option 'b' is present with argument $OPTARG
            ;;
        c)
            # Option 'c' is present
            ;;
        :)
            # Missing argument for an option
            ;;
        ?)
            # Invalid option
            ;;
    esac
done

Method 2: Using getopts with Long Options (GNU getopt)

optstring=":ab:c:"
longoptions="help,version"

# Parse options
getopt -o "$optstring" --long "$longoptions" -n 'script.sh' -- "$@" | while true; do
    case "$1" in
        -a)
            # Option 'a' is present
            ;;
        -b)
            # Option 'b' is present with argument $2
            shift
            ;;
        -c)
            # Option 'c' is present
            ;;
        --help)
            # Display help message
            ;;
        --version)
            # Display version information
            ;;
        --)
            shift
            break
            ;;
        *)
            echo "Invalid option: $1"
            break
            ;;
    esac
    shift
done

Method 3: Using getopts with Short and Long Options

while getopts ":ab:c:help" option; do
    case $option in
        a)
            # Option 'a' is present
            ;;
        b)
            # Option 'b' is present with argument $OPTARG
            ;;
        c)
            # Option 'c' is present
            ;;
        help)
            # Display help message
            ;;
        :)
            # Missing argument for an option
            ;;
        ?)
            # Invalid option
            ;;
    esac
done

Method 4: Using getopt with Short and Long Options (GNU getopt)

shortoptions="ab:c:"
longoptions="help,version"

# Parse options
parsed_options=$(getopt -o "$shortoptions" --long "$longoptions" -n 'script.sh' -- "$@")
eval set -- "$parsed_options"

while true; do
    case "$1" in
        -a)
            # Option 'a' is present
            ;;
        -b)
            # Option 'b' is present with argument $2
            shift
            ;;
        -c

)
            # Option 'c' is present
            ;;
        --help)
            # Display help message
            ;;
        --version)
            # Display version information
            ;;
        --)
            shift
            break
            ;;
        *)
            echo "Invalid option: $1"
            break
            ;;
    esac
    shift
done

Iterating over arguments

# Accessing arguments
arg1=$1
arg2=$2
arg3=$3

# Iterating over arguments
for arg in "$@"; do
    # Process each argument
done

Example Script

#!/bin/bash

while getopts ":ab:c:help" option; do
    case $option in
        a)
            echo "Option 'a' is present"
            ;;
        b)
            echo "Option 'b' is present with argument $OPTARG"
            ;;
        c)
            echo "Option 'c' is present"
            ;;
        help)
            echo "Displaying help message..."
            ;;
        :)
            echo "Missing argument for option -$OPTARG"
            ;;
        ?)
            echo "Invalid option -$OPTARG"
            ;;
    esac
done

shift $((OPTIND-1))

echo "Remaining arguments: $@"

Run script

./script.sh -a -b argument1 -c argument2 remaining_argument