(* -*- caml -*- *)

(* hello world *)
(* print a simple string on stdout *)
print_endline "Hello World"

(* argv *)
(* access command line parameters (no segmentation fault accepted, nor silent exception, so some languages must explicitly check the presence of the argument) *)
print_endline Sys.argv.(1)

(* env *)
(* access environment variable *)
print_endline(Sys.getenv "HOME")

(* test file exists *)
(* return exit code error (non zero) if a file does not exist *)
if not(Sys.file_exists "/etc/mtab") then exit 1

(* test file readable *)
(* return exit code error (non zero) if a file is not readable *)
try open_in("/etc/mtab") with _ -> exit 1

(* formatting *)
(* print integers in a simple formatted string *)
let a, b = 1, 2 in
Printf.printf "%d + %d = %d\n" a b (a + b)


(* system *)
(* call an external program and check the return value *)
if Sys.command "false" != 0 then prerr_endline("false failed");
ignore(Sys.command "echo done")


(* sed in place *)
(* remove #-comments from a file (modifying the file, i.e. in place) *)
let l = Std.input_list (open_in Sys.argv.(1)) in
let f = open_out Sys.argv.(0) in
List.iter (fun l -> output_string f 
 ((Str.replace_first (Str.regexp "#.*") "" l) ^"\n")) l;;


(* compile what must be *)
(* find and compile .c files into .o when the .o is old or absent *)
open Unix

let listdir dir =
  let rec listdir_ hdir =
    try
      let s = readdir hdir in
      if s = "." || s = ".." then
        listdir_ hdir
      else 
        s :: listdir_ hdir
    with End_of_file -> []
  in
  let hdir = opendir dir in
  let l = listdir_ hdir in
  closedir hdir ;
  l

let rec doit dir =
  List.iter (fun s ->
    let f = Filename.concat dir s in
    if (lstat f).st_kind = S_DIR then
      doit f
    else if Filename.check_suffix f ".c" then
      let o = Filename.chop_extension f ^ ".o" in
      if not (Sys.file_exists o && 
              (stat o).st_mtime > (stat f).st_mtime) then
        let cmd = Printf.sprintf "gcc -c -o '%s' '%s'" o f in
        print_endline ("compiling " ^ f ^ " to " ^ o) ;
        ignore (Sys.command cmd)
  ) (listdir dir)
;;
doit(".")


(* grep *)
(* grep with -F -i -h handling, usage, grep'ing many files *)
open List

let rec iter_lines f fd =
  try
    f (input_line fd) ; iter_lines f fd
  with End_of_file -> ()

let _ = 
  let i, fixed, usage = ref false, ref false, ref false in

  Arg.parse [ "-i", Arg.Set i, "" ; 
              "-F", Arg.Set fixed, "" ;
              "-h", Arg.Set usage, "" ;
            ] (fun _ -> ()) "" ;
  match filter (fun s -> s.[0] <> '-') (Array.to_list Sys.argv) with
  | _ :: r :: files when not !usage ->
      let r = if !fixed then Str.quote r else r in
      let re = (if !i then Str.regexp_case_fold else Str.regexp) r in
      let prefix = length files > 1 in

      iter (fun (name, fd) ->
        iter_lines (fun s ->
          try 
            let _ = Str.search_forward re s 0 in
            print_endline ((if prefix then name ^ ":" else "") ^ s)
          with Not_found -> ()
        ) fd
      ) (if files = [] then 
           ["", stdin] 
         else
           map (fun s -> s, open_in s) files)

  | _ ->
      prerr_endline "usage: grep [-F] [-i] regexp [files...]" ;
      exit 1