シェルスクリプトで関数をそのままサブコマンドとして使う

$ ./my_command.sh <subcommand> [options]

#!/usr/bin/env bash

# Default parameters
__name="Alice"

# Non sub command
_hello () {
  echo "hello $1!"
}

# sub commands
greet () {
  _hello "$__name"
}

commands () {
  echo "$__subcommands"
}

help () {
  echo "Usage $0 <subcommand> [options]"
  echo ""
  echo "Subcommands: $(commands)"
}

# Make sub command list
__subcommands=$(set | grep -v "^_" | grep -v "^ " | grep " () $" | cut -d' ' -f1 | tr '\n' ' ')

# Start main
if [ $# -eq 0 ];then
  help
fi

# Check sub command
__subcommand="$1"
shift

if ! echo " $__subcommands "|grep -q " $__subcommand ";then
  echo "$__subcommand is unknown subcommand."
  echo ""
  help
  exit 1
fi

# Get other arguments
while getopts n:h OPT;do
  case $OPT in
    "n")__name="$OPTARG";;
    "h")help; exit 0;;
    *) echo "Unknown argument: $OPT"; echo; help; exit 1;;
  esac
done

# Run sub command
$__subcommand

$ ./my_command.sh
Usage ./my_command.sh <subcommand> [options]

Subcommands: commands greet help
$ ./my_command.sh commands
commands greet help
$ ./my_command.sh help
Usage ./my_command.sh <subcommand> [options]

Subcommands: commands greet help
$ ./my_command.sh greet
hello Alice!
$ ./my_command.sh greet -n Bob
hello Bob!
$ ./my_command.sh abc
abc is unknown subcommand.

Usage ./my_command.sh <subcommand> [options]

Subcommands: commands greet help
$

__subcommands=$(set | grep " () $" | grep -v "^_" | grep -v "^ " | cut -d' ' -f1 | tr '\n' ' ')

greet () 
{ 
  _hello "$__name"
}

function greet
{
  _hello "$__name"
}

if ! echo " $__subcommands "|grep -q " $__subcommand ";then