{
  type token = ECHO | QUOTED of string | UNQUOTED of string | COMMENT
  exception Eof
}

let alphanum     = [ 'A'-'Z' 'a'-'z' '0'-'9' '_' ]
let comment_line = "//"([^ 'n' ]+)'n'
let space        = [ ' ' 't' 'n' ]
let quoted       = '"'([^ '"' ]+)'"'
let unquoted     = alphanum('/'?alphanum+)+

rule lexer = parse
  space+                      { lexer lexbuf }
| comment_line                { print_endline "got comment"; COMMENT }
| "echo"                      { ECHO }
| quoted                      { print_endline "got quoted"; QUOTED (Lexing.lexeme lexbuf) }
| unquoted                    { print_endline "got unquoted"; UNQUOTED (Lexing.lexeme lexbuf) }
| eof                         { raise Eof }

{

  let _ =
    try
      let lexbuf = Lexing.from_channel stdin in
      while true do
          match lexer lexbuf with
            ECHO -> print_endline "echo"
          | QUOTED _ -> print_endline "quoted"
          | UNQUOTED _ -> print_endline "unquoted"
          | COMMENT -> print_endline "comment"
      done
    with Eof -> exit 0

}