getopts - POSIX shell long options parser

This small shell library solves the issue of using long options in shell scripts that can only rely on a POSIX environment. It is drop-in compatible with the standard getopts, except for $OPTIND. The specification grammar for long options is derived from Solaris and extremely simple to use.

Usage

• Copy-paste the getopts.sh script into your own code, or include it with git submodule. This last method has two advantages: updates, and you can verify that it works with test.sh.

• Change your getopts calls from getopts OPT_VAR ":opt:s:" to getopts OPT_VAR:OPTIND_ALTERNATIVE ":opt:s:" "$@" - i.e., add a colon and variable name for the position to the first argument, and explicitly pass the arguments you want to be parsed. This of course means that you also have to replace all occurences of OPTIND with your alternative.

• Test! The changes you made should change nothing at this point, which is quite easy to test.

• Now add the long options. The grammar for long options is the one Solaris uses for their getopts implementation. But you don't have to read their documentation, as it is very simple. Long options are synonyms for short options, and come after them (and the optional colon for an argument). So, to give an example:

   getopts OPT 'f:av'
  

  becomes

   getopts OPT:INDEX 'f:(file)a(append)v(verbose)' "$@"
  

  and the parsing for the OPT variable can stay the same, as it outputs the single-letter synonym for every long option encountered.

Bugs

• OPTIND does not work. This will never be fixed. I tried a lot of things, but it boils down to the simple fact that this one variable can't hold the full state of getopts, as it needs to remember at which character in the argument it is (e.g. tar -xf foo.tar, first argument, but x or f?). And using an extra variable does not work either. In that case, how do you discriminate between being in the first argument, or being reset?
• Verbose mode isn't added yet. Don't think anyone cares.