bash-getopt

Examples of parsing command line arguments in BASH

mk_opt

This script attempts to encapsulate the complicated parts of getopt. All command line options can be specified using a function call.

	# Table of command line options and their callbacks
	mk_opt "a" "arga"   ":"  "<N>"  "This has a required argument"  "export VALUE_A="
	mk_opt "b" "argb"   "::" "[X]"  "This has an optional argument"
	mk_opt "c" "argc"   ""   ""     "This has no argument" "true #Hacky no-op callback "
	mk_opt ""  "argd"   ":"   "<N>" "This has no shorthand" 
	mk_opt "h" "help"   ""   ""     "Display this help text"

This provides parsing and validation, as well as a nice usage function.

	~/code/bash-getopt$ ./mk_opt --help
	  Usage: mk_opt [options]
          
          Example usage text.
	  
	  Options:
	     -a --arga <N>    This has a required argument
	     -b --argb [X]    This has an optional argument
	     -c --argc        This has no argument
		--argd <N>    This has no shorthand
	     -h --help        Display this help text

Features

• Supports long and short parameters (-h and --help)
• Supports optional argument values
• Triggers a callback for each parameter provided by the user
• Consolidates the configuration of parameters into a one-line call for each parameter

Drawbacks

It may be much simpler to specify the command line options using mk_opt, but the rest of the code is not simpler at all. This approach is probably not worth taking. I'm posting it here merely for reference. A template script should never be this complicated.

Bugs

I have no intention of fixing any bugs in this. I have seen a few oddities;

• Optional arguments must have =. ** Bad: ~/code/bash-getopt$ ./mk_opt -argb 2 ** Good: ~/code/bash-getopt$ ./mk_opt -argb=2
• Providing a value for a parameter that does not allow a value results in misleading errors