playing around with a little bash subcommand environment

prog

#!/bin/bash

cmd-hello() {
  declare desc="Displays a friendly hello"
  declare firstname="$1" lastname="$2"
  echo "Hello, $firstname $lastname."
}

cmd-help() {
  declare desc="Shows help information for a command"
  declare command="$1" showsource="${2:-true}"
  if [[ "$command" ]]; then
    echo "$command $(extract-args $command)"
    echo "  $(extract-desc $command)"
    echo
    if [[ "$showsource" = "true" ]]; then
      type cmd-$command | tail -n +2
      echo
    fi
  else
    echo; for cmd in $(list-cmds); do cmd-help $cmd false; done
  fi
}

extract-args() {
  local line=$(type cmd-$1 | grep declare | grep -v "declare desc" | head -1)
  echo -e "${line// /\n}" | awk -F= '/=/{print "<"$1">"}' | tr "\n" " "
}

extract-desc() {
  eval "$(type cmd-$1 | grep desc | head -1)"; echo $desc
}

list-cmds() {
  declare -F | grep "\-f cmd-" | awk -Fcmd- '{print $2}'
}

main() {
  local cmd="$1"; shift || true
  if type cmd-$cmd &> /dev/null; then
    cmd-$cmd $@
  else
    echo "No such command: $cmd"
    echo
    echo "Available commands:"
    list-cmds | sed "s/^/  /"
    echo
    exit 2
  fi
}

main $@

prog_example

$ ./prog
No such command: 

Available commands:
  hello
  help

$ ./prog help

hello <firstname> <lastname> 
  Displays a friendly hello

help <command> <showsource> 
  Shows help information for a command

$ ./prog hello Jeff Lindsay
Hello, Jeff Lindsay.

$ ./prog help hello
hello <firstname> <lastname> 
  Displays a friendly hello

cmd-hello () 
{ 
    declare desc="Displays a friendly hello";
    declare firstname="$1" lastname="$2";
    echo "Hello, $firstname $lastname."
}