#!/bin/raykov to code or not to code...

About Code Maintainability

03 Oct 2014

Have you ever played with command line arguments in shell scripting (Bash)? One day I decided to write a simple script that I would paste in my doings and use it to parse arguments instead of sourcing one.

The thing is, there is no standard way of doing it. There is getopt but it doesn't support long argument names, unless you use the GNU one. But then it becomes less portable and you can't easily define mandatory arguments. That's why I came up with this:

#!/usr/bin/env bash

# Console-line parameter parsing script.
# Specify options in the OPTS variable in the following format:
# whitespace sepparated values
# OPTS="--<argument_name> --<argument_with_value>= --!<mandatory_argument>="
# Then it creates variables in the format: OPTS_<ARGUMENT_NAME_IN_CAPS>
# If the argument doesn't need value to be provided assings 0 or 1.
# If the argument needs value but none is provided a 0 is assigned

#SCRIPT START
OPTS="--argument --anotherarg --!thirdarg= --fourtharg="

IFS='--' read -ra args <<< "$OPTS" && for i in "${args[@]}"; do
   if [ ! -z $i ]; then
      ARG_NAME="${i//[=! ]/}"
      ARG_VALUE=$(printf -- '%s\n' "${@}" | grep -- "--$ARG_NAME")
      if [[ "$i" =~ ^.*=\ ?$ ]]; then
         if [ -z "${ARG_VALUE##--$i}" ]; then
            [[ "$i" == *!* ]] && echo "$ARG_NAME is mandatory!" && exit 1
            printf -v "OPTS_${ARG_NAME^^}" "0"
         else
            printf -v "OPTS_${ARG_NAME^^}" "${ARG_VALUE##--$ARG_NAME=}"
         fi
      else
         [ -z "${ARG_VALUE##--$i}" ] ; ARG_VALUE=$?
         printf -v "OPTS_${ARG_NAME^^}" "$ARG_VALUE"
      fi
   fi
done
# SCRIPT END


echo "OPTS_ARGUMENT: $OPTS_ARGUMENT"
echo "OPTS_ANOTHERARG: $OPTS_ANOTHERARG"
echo "OPTS_THIRDARG: $OPTS_THIRDARG"
echo "OPTS_FOURTHARG: $OPTS_FOURTHARG"

What's wrong

It's great for what it does. It lets me define arguments in a simple manner, having args with value and mandatory ones. But then, 1 month later I had to edit it and then I remembered all the articles about code maintainability I've seen. The beest thing I could do is write one myself. I'll even not go into any reasoning for mainainable code.

There it is, the code snippet - all the reasoning you need.