[diablerouge]

This seems like a neat sed trick, but I'm not sure that it's useful for this particular case?

When I write a shell script, I often write a help function if it's not a totally trivial script, but there's no need for this cryptic sed expression, right? You can just call `echo` a few times and do it the obvious way. That works better for maintainability and if you put it at the top of the file then it's immediately visible when opening or using `head` on it.

Neat trick though - sed is super useful for all kinds of things. I had a co-worker who bound a keybinding to a sed one-liner that would automagically reconfigure some files that needed to be changed regularly. I ended up using that trick to allow for changing my terminal console colorscheme with a single command.

[e12e]

It's a little sad that standard shell here documents only support elliding leading tabs (it wouldn't be so sad if the record separator hadn't been thrown under the bus - having a character for indentation distinct from space is good... In theory).

But at any rate my typical usage() is generally along these lines (warning watch out for expansions):

  usage()
  {
    cat - <<-EOF
    `basename ${0}`: demonstrate here docs
     Usage:
     `basename ${0}` <required argument> [-o|--optional-param] 

       Etc. Possibly referencing
       default value: ${DEFAULT_VALUE}
    EOF
  }

[jolmg]

I think it'd be better without using basename, just $0. That way it matches the way it was called, which is how the user chose to access it for whatever reason. The bare filename might refer to a different command, even. Also, if you include examples in the help text, they'll also be able to copy and paste, instead of having to manually insert what basename stripped away.

[e12e]

True enough - I find it depends a bit on the nature of the script - if it's something buried under misc/tools/extra/bin/util.sh - i tend to prefer brevity - especially in the first paragraph/usage section (util.sh <required param> [optional param]).

But for more concrete examples I'll often leave off the basename - for easier cut and paste.

[zzzcpan]

Right, it's a bit useless trick. I guess the author is just exploring how to organize help, maybe thinking about larger scripts or maybe doing it for the article. Either way it's hard to see it going anywhere with sed. If you were to explore parsing and organizing help, I'd suggest starting with a simple pure shell loop like this:

   while read -r line; do
      case "$line" in 
      "###"*) 
         echo "${line#\###}" ;;
      esac
   done <"$0"