An attempt at summarizing the right way to use POSIX-compliant getopts.

A couple links:

• https://pubs.opengroup.org/onlinepubs/9699919799/utilities/getopts.html
  • https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap12.html#tag_12_02
• https://sookocheff.com/post/bash/parsing-bash-script-arguments-with-shopts/

First, there has been much blood spilled discussing how to support optional arguments using getopts – the correct solution is to not do that, as explained in Guideline 7 here.