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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. So we won't.

And, second, if the optstring handed to getopts starts with a colon, then getopts uses what is called “silent error reporting”; this appears to be the recommended approach, so we'll stick with that. In short, don't do this:

while getopts ab:c: opt ; do

Do this (note the leading colon):

while getopts :ab:c: opt ; do

Explanation below.

... coming soon ...