how to set usage/help message for errors (e.g. Unrecognized option: -optionx)

[geneliu]

Is there a way to add/overwrite the error handling function with usage (so it print out the help message)?

error() {
	case $2 in
		unknown) echo "$1" ;;
		number:*) echo "Not a number: $3" ;;
		range:1) echo "Not a number: $3" ;;
		range:2) echo "Out of range ($5 - $6): $3"; return 2 ;;
		regex:*) echo "Not a valid input: $3" ;;
		*) return 0 ;; # Display default error
	esac
	return 1
}

e.g.: cmd.sh -optionX will print out the default "Unrecognized option: ...". Can this be enhanced with print out as the same from cmd.sh -h (usage usually) instead?

[ko1nksm]

Is this what you mean?

parser_definition() {
  setup   REST help:usage error:error
  ...
}

error() {
	usage
	return 1 # if you want to suppress the default message
}

Alternative

parser_definition() {
  setup   REST help:usage error:usage # <---
  # Use `error:"usage && false"` if you want to suppress the default message
  ...
}

# no error handler

[geneliu]

Thanks @ko1nksm !