I once created a set of shell functions which I wanted to have a docstring-like functionality. The solution I came up with was to have each shell function start with the : command with a string as an argument. Since : is an actual command, not a comment, it was preserved as part of the function, and could be extracted at runtime using relatively simple parsing to do introspection.

Example:

  foo(){
    : "This is a docstring for the foo() function"
    bar --verbose | baz --quiet
  }

For those who don’t know: ":" is a shell built-in command which does nothing and ignores all arguments. It was the way in which shell scripts had comments before the modern syntax of using # for comments was introduced.