Bash / Shell named arguments parsing

gistfile1.txt

#!/bin/bash -e

## Default var values
declare arg1=""
declare arg2=""

## parse positional args
while [ $# -gt 0 ]; do
    if [[ $1 == "--help" ]]
    then
        echo "INFO: Open the script, check the examples section."
        exit 0
    elif [[ $1 == "--"* ]]
    then
        if [[ "$2" == "" ]]
        then
            printf "ERR: Argument '%s' has no value. Exiting with error.\n" "${1}"
            exit 1
        fi

        key="${1/--/}"
        declare "$key"="$2"
        shift
    fi
    shift
done

# output positional args
echo "Positional argument key values: arg1: ${arg1} arg2: ${arg2}"