Argparse For Shell Scripts

In a nutshell

Use Python’s argparse in any shell scripts.

In Detail

Python’s argparse is a great tool for creating command line interfaces. It is very easy to use and provides a lot of functionality out of the box. It also provides a way to generate automatic help from the argument specification. It benifits from a wide range of third party packages that extend its functionality and huge user base that can help you with any problems you might face.

Shell scripts on the other hand suffer in this area. While there are ways to parse command line arguments in shell scripts like bash etc. they do not offer so many capabilities as Python’s argparse, as simple as argument type validation or automatic help generation.

Instead of reinventing the wheel for different shell scripting languages, this package provides a way to reuse the existing Python’s argparse package in shell scripts and get all the functionalities built into it in any shell scripting language of your choice.

All you need to do is to write your argument specification in Python like you do for any python script and do a one line black magic in your shell script, boom! you have all the power of Python’s argparse in your shell script.

If you are not familiar with Python’s argparse package, here is how it looks like:

import argparse

def getArgParser():
    'Define and return the argparse object'

    parser = argparse.ArgumentParser(description='Sample argparse argument parser')
    parser.add_argument('-i', '--integer', type=int, default=10, help='Integer')
    parser.add_argument('-s', '--string', type=str, required=True, help='String')
    parser.add_argument('-l', '--list', type=str, nargs='+', help='List of Strings')
    return parser

if __name__ == '__main__':
    args = getArgParser().parse_args()

Now, to use this in your shell script, you need to do the following:

Import argparse_enh package.
Instead of calling the parse_args(), call ape.dumpArgs(getArgParser())
eval the output of the Python script in your shell script.

Modified Python code looks like below

import argparse
import argparse_enh.argparse_enh as ape

def getArgParser():
    'Define and return the argparse object'

    parser = argparse.ArgumentParser(description='Sample argparse argument parser')
    parser.add_argument('-i', '--integer', type=int, default=10, help='Integer')
    parser.add_argument('-s', '--string', type=str, required=True, help='String')
    parser.add_argument('-l', '--list', type=str, nargs='+', help='List of Strings')
    return parser

if __name__ == '__main__':
    ape.dumpArgs(getArgParser())

Add below like of code or equivalent in your shell script.

#!/bin/bash

# Parse the arguments using Python's argparse_enh
eval $(sample_argparser.py "$@")

# Print the parsed arguments
echo $opt_integer

All the options will be available as variables prefixed with opt_.