Simple process runner (Ocaml)

simpleproc.ml

(** Compile with:

    [ocamlc -c simpleproc.ml]
    [ocamlc -o simpleproc.byte unix.cmo simpleproc.cmo]

    Run it:

    [./simpleproc.byte "ls -la"]

    *)

module Buff = struct

  let create = Buffer.create 32
  let dump b = Buffer.contents b
  let read_all b c =
    try
      while true do
        Buffer.add_channel b c 1
      done
    with End_of_file -> ()

end

module Proc = struct

  let popen = Unix.open_process_full
  let pclose = Unix.close_process_full
  let int_of_status s =
    match s with
    | Unix.WEXITED r -> r
    | Unix.WSIGNALED r -> r
    | Unix.WSTOPPED r -> r

end

module Cmd = struct

  let proc cmd env out_buf err_buf =
    let out_ch, in_ch, err_ch = Proc.popen cmd env in
    ignore (Buff.read_all out_buf out_ch);
    ignore (Buff.read_all err_buf err_ch);
    let s = Proc.pclose (out_ch, in_ch, err_ch) in
    let c = Proc.int_of_status s in
    (c, Buff.dump out_buf, Buff.dump err_buf)

end

let main () =
  let cmd = Sys.argv.(1) in
  let env = [|"foo=bar"|] in
  let out_buf = Buffer.create 32 and
      err_buf = Buffer.create 32 in

  let exit_code, out, err = Cmd.proc cmd env out_buf err_buf in

  print_endline "------ stdout";
  print_endline out;
  print_endline "------ stderr";
  print_endline err;
  print_endline "------ exit code";
  print_endline (string_of_int exit_code)

let () = Unix.handle_unix_error main ()