gem_completion.sh

_gem()
{
  if [[ -z $__gem_commands ]] ; then
    __gem_commands=$(gem help commands | grep '^    [a-z]' | cut -d " " -f 5)
  fi

  local cur prev opts base
  COMPREPLY=()
  cur="${COMP_WORDS[COMP_CWORD]}"
  prev="${COMP_WORDS[COMP_CWORD-1]}"

  case "${prev}" in
    open|read)
      if [[ -z $__installed_gems ]] ; then
        __installed_gems=$(gem list | grep '^[A-Za-z]' | cut -d " " -f 1)
      fi
      COMPREPLY=($(compgen -W "${__installed_gems}" -- ${cur}))
      return 0;
      ;;
    gem)
      ;;
    *)
      COMPREPLY=($(compgen -o default))
      return 0;
      ;;
  esac

  COMPREPLY=($(compgen -W "${__gem_commands}" -- ${cur}))
  return 0; 
}


complete -F _gem gem