Bash argument parser

parse_args.sh

#!/usr/bin/env bash

#
# An over-engineered bash argument parser
# Inspired from *args and **kwargs in Python
#
# Usage:
#   parse_args "$@"
#
# Examples:
#   script.sh 10 20
#     args: [10, 20]
#     kwargs: []
#   script.sh --foo bar --baz qux 10 20
#     args: [10, 20]
#     kwargs: [foo: bar, baz: qux]
#   script.sh -x 3 -y 2 -z -- 10 20
#     args: [10, 20]
#     kwargs: [x: 3, y: 2, z: 1]
#

declare -a args
declare -A kwargs

function is_value () {
    if [[ $(echo $1 | grep -cE "^-") = 0 ]]; then
        return 0
    fi
    return 1
}

function parse_args () {
    local arg
    local value

    while [[ $# -gt 0 ]]; do
        if [[ $1 = "--" ]]; then
            shift; continue
        elif $(is_value $1); then
            arg=$1
        else
            arg=$(echo $1 | sed -nE "s/--?(.*)/\1/p")
        fi

        if [[ ! -z ${2+_} ]] && $(is_value $2) && ! $(is_value $1); then
            kwargs[$arg]=$2
            shift
        elif ! $(is_value $1); then
            kwargs[$arg]=1
        else
            args+=($arg)
        fi
        shift
    done
}