bash_command_not_found

# source from .bashrc for lazy pipe grep magic

command_not_found_handle () 
{ 
  # only run within an input pipe
  if [[ -p /dev/stdin ]]; then 
    grep -- "$*"
    return $?
  fi

  echo $"$1: command not found"
  return 127
}

You prob only want to pass one argument to grep -- the string to search for. With "$@" you pass all the original args separately, so if you had more than one word they would be interpreted as file names to look in. I think "$*" makes more sense so you pass just one single arg to grep consisting of all the words you had after the pipe.

Also makes sense to pass -- first in case your string starts with a hyphen -- this way it won't be treated as an arg.

So like

grep -- "$*"

Yeah, thanks a lot @algorythmic. From time to time, I still use the args passing feature, but if i really need those I can still pipe and call grep directly.