ocaml/otherlibs/unix/unix.ml

(***********************************************************************)
(*                                                                     *)
(*                           Objective Caml                            *)
(*                                                                     *)
(*            Xavier Leroy, projet Cristal, INRIA Rocquencourt         *)
(*                                                                     *)
(*  Copyright 1996 Institut National de Recherche en Informatique et   *)
(*  en Automatique.  All rights reserved.  This file is distributed    *)
(*  under the terms of the GNU Library General Public License, with    *)
(*  the special exception on linking described in file ../../LICENSE.  *)
(*                                                                     *)
(***********************************************************************)

(* $Id$ *)

type error =
    E2BIG
  | EACCES
  | EAGAIN
  | EBADF
  | EBUSY
  | ECHILD
  | EDEADLK
  | EDOM
  | EEXIST
  | EFAULT
  | EFBIG
  | EINTR
  | EINVAL
  | EIO
  | EISDIR
  | EMFILE
  | EMLINK
  | ENAMETOOLONG
  | ENFILE
  | ENODEV
  | ENOENT
  | ENOEXEC
  | ENOLCK
  | ENOMEM
  | ENOSPC
  | ENOSYS
  | ENOTDIR
  | ENOTEMPTY
  | ENOTTY
  | ENXIO
  | EPERM
  | EPIPE
  | ERANGE
  | EROFS
  | ESPIPE
  | ESRCH
  | EXDEV
  | EWOULDBLOCK
  | EINPROGRESS
  | EALREADY
  | ENOTSOCK
  | EDESTADDRREQ
  | EMSGSIZE
  | EPROTOTYPE
  | ENOPROTOOPT
  | EPROTONOSUPPORT
  | ESOCKTNOSUPPORT
  | EOPNOTSUPP
  | EPFNOSUPPORT
  | EAFNOSUPPORT
  | EADDRINUSE
  | EADDRNOTAVAIL
  | ENETDOWN
  | ENETUNREACH
  | ENETRESET
  | ECONNABORTED
  | ECONNRESET
  | ENOBUFS
  | EISCONN
  | ENOTCONN
  | ESHUTDOWN
  | ETOOMANYREFS
  | ETIMEDOUT
  | ECONNREFUSED
  | EHOSTDOWN
  | EHOSTUNREACH
  | ELOOP
  | EOVERFLOW
  | EUNKNOWNERR of int

exception Unix_error of error * string * string

let _ = Callback.register_exception "Unix.Unix_error"
                                    (Unix_error(E2BIG, "", ""))

external error_message : error -> string = "unix_error_message"

let handle_unix_error f arg =
  try
    f arg
  with Unix_error(err, fun_name, arg) ->
    prerr_string Sys.argv.(0);
    prerr_string ": \"";
    prerr_string fun_name;
    prerr_string "\" failed";
    if String.length arg > 0 then begin
      prerr_string " on \"";
      prerr_string arg;
      prerr_string "\""
    end;
    prerr_string ": ";
    prerr_endline (error_message err);
    exit 2

external environment : unit -> string array = "unix_environment"
external getenv: string -> string = "sys_getenv"
external putenv: string -> string -> unit = "unix_putenv"

type process_status =
    WEXITED of int
  | WSIGNALED of int
  | WSTOPPED of int

type wait_flag =
    WNOHANG
  | WUNTRACED

external execv : string -> string array -> 'a = "unix_execv"
external execve : string -> string array -> string array -> 'a = "unix_execve"
external execvp : string -> string array -> 'a = "unix_execvp"
external execvpe : string -> string array -> string array -> 'a = "unix_execvpe"
external fork : unit -> int = "unix_fork"
external wait : unit -> int * process_status = "unix_wait"
external waitpid : wait_flag list -> int -> int * process_status = "unix_waitpid"
external getpid : unit -> int = "unix_getpid"
external getppid : unit -> int = "unix_getppid"
external nice : int -> int = "unix_nice"

type file_descr = int

let stdin = 0
let stdout = 1
let stderr = 2

type open_flag =
    O_RDONLY
  | O_WRONLY
  | O_RDWR
  | O_NONBLOCK
  | O_APPEND
  | O_CREAT
  | O_TRUNC
  | O_EXCL
  | O_NOCTTY
  | O_DSYNC
  | O_SYNC
  | O_RSYNC

type file_perm = int


external openfile : string -> open_flag list -> file_perm -> file_descr
           = "unix_open"

external close : file_descr -> unit = "unix_close"
external unsafe_read : file_descr -> string -> int -> int -> int = "unix_read"
external unsafe_write : file_descr -> string -> int -> int -> int = "unix_write"

let read fd buf ofs len =
  if ofs < 0 || len < 0 || ofs > String.length buf - len
  then invalid_arg "Unix.read"
  else unsafe_read fd buf ofs len
let write fd buf ofs len =
  if ofs < 0 || len < 0 || ofs > String.length buf - len
  then invalid_arg "Unix.write"
  else unsafe_write fd buf ofs len

external in_channel_of_descr : file_descr -> in_channel
                             = "caml_open_descriptor_in"
external out_channel_of_descr : file_descr -> out_channel
                              = "caml_open_descriptor_out"
external descr_of_in_channel : in_channel -> file_descr = "channel_descriptor"
external descr_of_out_channel : out_channel -> file_descr
                              = "channel_descriptor"

type seek_command =
    SEEK_SET
  | SEEK_CUR
  | SEEK_END

external lseek : file_descr -> int -> seek_command -> int = "unix_lseek"
external truncate : string -> int -> unit = "unix_truncate"
external ftruncate : file_descr -> int -> unit = "unix_ftruncate"

type file_kind =
    S_REG
  | S_DIR
  | S_CHR
  | S_BLK
  | S_LNK
  | S_FIFO
  | S_SOCK

type stats =
  { st_dev : int;
    st_ino : int;
    st_kind : file_kind;
    st_perm : file_perm;
    st_nlink : int;
    st_uid : int;
    st_gid : int;
    st_rdev : int;
    st_size : int;
    st_atime : float;
    st_mtime : float;
    st_ctime : float }

external stat : string -> stats = "unix_stat"
external lstat : string -> stats = "unix_lstat"
external fstat : file_descr -> stats = "unix_fstat"
external unlink : string -> unit = "unix_unlink"
external rename : string -> string -> unit = "unix_rename"
external link : string -> string -> unit = "unix_link"

module LargeFile =
  struct
    external lseek : file_descr -> int64 -> seek_command -> int64 = "unix_lseek_64"
    external truncate : string -> int64 -> unit = "unix_truncate_64"
    external ftruncate : file_descr -> int64 -> unit = "unix_ftruncate_64"
    type stats =
      { st_dev : int;
        st_ino : int;
        st_kind : file_kind;
        st_perm : file_perm;
        st_nlink : int;
        st_uid : int;
        st_gid : int;
        st_rdev : int;
        st_size : int64;
        st_atime : float;
        st_mtime : float;
        st_ctime : float;
      }
    external stat : string -> stats = "unix_stat_64"
    external lstat : string -> stats = "unix_lstat_64"
    external fstat : file_descr -> stats = "unix_fstat_64"
  end

type access_permission =
    R_OK
  | W_OK
  | X_OK
  | F_OK

external chmod : string -> file_perm -> unit = "unix_chmod"
external fchmod : file_descr -> file_perm -> unit = "unix_fchmod"
external chown : string -> int -> int -> unit = "unix_chown"
external fchown : file_descr -> int -> int -> unit = "unix_fchown"
external umask : int -> int = "unix_umask"
external access : string -> access_permission list -> unit = "unix_access"

external dup : file_descr -> file_descr = "unix_dup"
external dup2 : file_descr -> file_descr -> unit = "unix_dup2"
external set_nonblock : file_descr -> unit = "unix_set_nonblock"
external clear_nonblock : file_descr -> unit = "unix_clear_nonblock"
external set_close_on_exec : file_descr -> unit = "unix_set_close_on_exec"
external clear_close_on_exec : file_descr -> unit = "unix_clear_close_on_exec"

external mkdir : string -> file_perm -> unit = "unix_mkdir"
external rmdir : string -> unit = "unix_rmdir"
external chdir : string -> unit = "unix_chdir"
external getcwd : unit -> string = "unix_getcwd"
external chroot : string -> unit = "unix_chroot"

type dir_handle

external opendir : string -> dir_handle = "unix_opendir"
external readdir : dir_handle -> string = "unix_readdir"
external rewinddir : dir_handle -> unit = "unix_rewinddir"
external closedir : dir_handle -> unit = "unix_closedir"

external pipe : unit -> file_descr * file_descr = "unix_pipe"
external symlink : string -> string -> unit = "unix_symlink"
external readlink : string -> string = "unix_readlink"
external mkfifo : string -> file_perm -> unit = "unix_mkfifo"
external select :
  file_descr list -> file_descr list -> file_descr list -> float ->
        file_descr list * file_descr list * file_descr list = "unix_select"

type lock_command =
    F_ULOCK
  | F_LOCK
  | F_TLOCK
  | F_TEST
  | F_RLOCK
  | F_TRLOCK

external lockf : file_descr -> lock_command -> int -> unit = "unix_lockf"
external kill : int -> int -> unit = "unix_kill"
type sigprocmask_command = SIG_SETMASK | SIG_BLOCK | SIG_UNBLOCK
external sigprocmask: sigprocmask_command -> int list -> int list
        = "unix_sigprocmask"
external sigpending: unit -> int list = "unix_sigpending"
external sigsuspend: int list -> unit = "unix_sigsuspend"

let pause() =
  let sigs = sigprocmask SIG_BLOCK [] in sigsuspend sigs

type process_times =
  { tms_utime : float;
    tms_stime : float;
    tms_cutime : float;
    tms_cstime : float }

type tm =
  { tm_sec : int;
    tm_min : int;
    tm_hour : int;
    tm_mday : int;
    tm_mon : int;
    tm_year : int;
    tm_wday : int;
    tm_yday : int;
    tm_isdst : bool }

external time : unit -> float = "unix_time"
external gettimeofday : unit -> float = "unix_gettimeofday"
external gmtime : float -> tm = "unix_gmtime"
external localtime : float -> tm = "unix_localtime"
external mktime : tm -> float * tm = "unix_mktime"
external alarm : int -> int = "unix_alarm"
external sleep : int -> unit = "unix_sleep"
external times : unit -> process_times = "unix_times"
external utimes : string -> float -> float -> unit = "unix_utimes"

type interval_timer =
    ITIMER_REAL
  | ITIMER_VIRTUAL
  | ITIMER_PROF

type interval_timer_status =
  { it_interval: float;                 (* Period *)
    it_value: float }                   (* Current value of the timer *)

external getitimer: interval_timer -> interval_timer_status = "unix_getitimer"
external setitimer:
  interval_timer -> interval_timer_status -> interval_timer_status
  = "unix_setitimer"

external getuid : unit -> int = "unix_getuid"
external geteuid : unit -> int = "unix_geteuid"
external setuid : int -> unit = "unix_setuid"
external getgid : unit -> int = "unix_getgid"
external getegid : unit -> int = "unix_getegid"
external setgid : int -> unit = "unix_setgid"
external getgroups : unit -> int array = "unix_getgroups"

type passwd_entry =
  { pw_name : string;
    pw_passwd : string;
    pw_uid : int;
    pw_gid : int;
    pw_gecos : string;
    pw_dir : string;
    pw_shell : string }

type group_entry =
  { gr_name : string;
    gr_passwd : string;
    gr_gid : int;
    gr_mem : string array }


external getlogin : unit -> string = "unix_getlogin"
external getpwnam : string -> passwd_entry = "unix_getpwnam"
external getgrnam : string -> group_entry = "unix_getgrnam"
external getpwuid : int -> passwd_entry = "unix_getpwuid"
external getgrgid : int -> group_entry = "unix_getgrgid"

type inet_addr

external inet_addr_of_string : string -> inet_addr
                                    = "unix_inet_addr_of_string"
external string_of_inet_addr : inet_addr -> string
                                    = "unix_string_of_inet_addr"

let inet_addr_any = inet_addr_of_string "0.0.0.0"

type socket_domain =
    PF_UNIX
  | PF_INET

type socket_type =
    SOCK_STREAM
  | SOCK_DGRAM
  | SOCK_RAW
  | SOCK_SEQPACKET

type sockaddr =
    ADDR_UNIX of string
  | ADDR_INET of inet_addr * int

type shutdown_command =
    SHUTDOWN_RECEIVE
  | SHUTDOWN_SEND
  | SHUTDOWN_ALL

type msg_flag =
    MSG_OOB
  | MSG_DONTROUTE
  | MSG_PEEK

type socket_bool_option =
    SO_DEBUG
  | SO_BROADCAST
  | SO_REUSEADDR
  | SO_KEEPALIVE
  | SO_DONTROUTE
  | SO_OOBINLINE
  | SO_ACCEPTCONN

type socket_int_option =
    SO_SNDBUF
  | SO_RCVBUF
  | SO_ERROR
  | SO_TYPE
  | SO_RCVLOWAT
  | SO_SNDLOWAT

type socket_optint_option = SO_LINGER

type socket_float_option =
    SO_RCVTIMEO
  | SO_SNDTIMEO

external socket : socket_domain -> socket_type -> int -> file_descr
                                  = "unix_socket"
external socketpair :
        socket_domain -> socket_type -> int -> file_descr * file_descr
                                  = "unix_socketpair"
external accept : file_descr -> file_descr * sockaddr = "unix_accept"
external bind : file_descr -> sockaddr -> unit = "unix_bind"
external connect : file_descr -> sockaddr -> unit = "unix_connect"
external listen : file_descr -> int -> unit = "unix_listen"
external shutdown : file_descr -> shutdown_command -> unit = "unix_shutdown" 
external getsockname : file_descr -> sockaddr = "unix_getsockname"
external getpeername : file_descr -> sockaddr = "unix_getpeername"

external unsafe_recv :
  file_descr -> string -> int -> int -> msg_flag list -> int
                                  = "unix_recv"
external unsafe_recvfrom :
  file_descr -> string -> int -> int -> msg_flag list -> int * sockaddr
                                  = "unix_recvfrom"
external unsafe_send :
  file_descr -> string -> int -> int -> msg_flag list -> int
                                  = "unix_send"
external unsafe_sendto :
  file_descr -> string -> int -> int -> msg_flag list -> sockaddr -> int
                                  = "unix_sendto" "unix_sendto_native"

let recv fd buf ofs len flags =
  if ofs < 0 || len < 0 || ofs > String.length buf - len
  then invalid_arg "Unix.recv"
  else unsafe_recv fd buf ofs len flags
let recvfrom fd buf ofs len flags =
  if ofs < 0 || len < 0 || ofs > String.length buf - len
  then invalid_arg "Unix.recvfrom"
  else unsafe_recvfrom fd buf ofs len flags
let send fd buf ofs len flags =
  if ofs < 0 || len < 0 || ofs > String.length buf - len
  then invalid_arg "Unix.send"
  else unsafe_send fd buf ofs len flags
let sendto fd buf ofs len flags addr =
  if ofs < 0 || len < 0 || ofs > String.length buf - len
  then invalid_arg "Unix.sendto"
  else unsafe_sendto fd buf ofs len flags addr

external getsockopt : file_descr -> socket_bool_option -> bool
                                          = "unix_getsockopt_bool"
external setsockopt : file_descr -> socket_bool_option -> bool -> unit
                                          = "unix_setsockopt_bool"
external getsockopt_int : file_descr -> socket_int_option -> int
                                          = "unix_getsockopt_int"
external setsockopt_int : file_descr -> socket_int_option -> int -> unit
                                          = "unix_setsockopt_int"
external getsockopt_optint : file_descr -> socket_optint_option -> int option
                                          = "unix_getsockopt_optint"
external setsockopt_optint : file_descr -> socket_optint_option -> int option -> unit
                                          = "unix_setsockopt_optint"
external getsockopt_float : file_descr -> socket_float_option -> float
                                          = "unix_getsockopt_float"
external setsockopt_float : file_descr -> socket_float_option -> float -> unit
                                          = "unix_setsockopt_float"

type host_entry =
  { h_name : string;
    h_aliases : string array;
    h_addrtype : socket_domain;
    h_addr_list : inet_addr array }

type protocol_entry =
  { p_name : string;
    p_aliases : string array;
    p_proto : int }

type service_entry =
  { s_name : string;
    s_aliases : string array;
    s_port : int;
    s_proto : string }

external gethostname : unit -> string = "unix_gethostname"
external gethostbyname : string -> host_entry = "unix_gethostbyname"
external gethostbyaddr : inet_addr -> host_entry = "unix_gethostbyaddr"
external getprotobyname : string -> protocol_entry
                                         = "unix_getprotobyname"
external getprotobynumber : int -> protocol_entry
                                         = "unix_getprotobynumber"
external getservbyname : string -> string -> service_entry
                                         = "unix_getservbyname"
external getservbyport : int -> string -> service_entry
                                         = "unix_getservbyport"
type terminal_io = {
    mutable c_ignbrk: bool;
    mutable c_brkint: bool;
    mutable c_ignpar: bool;
    mutable c_parmrk: bool;
    mutable c_inpck: bool;
    mutable c_istrip: bool;
    mutable c_inlcr: bool;
    mutable c_igncr: bool;
    mutable c_icrnl: bool;
    mutable c_ixon: bool;
    mutable c_ixoff: bool;
    mutable c_opost: bool;
    mutable c_obaud: int;
    mutable c_ibaud: int;
    mutable c_csize: int;
    mutable c_cstopb: int;
    mutable c_cread: bool;
    mutable c_parenb: bool;
    mutable c_parodd: bool;
    mutable c_hupcl: bool;
    mutable c_clocal: bool;
    mutable c_isig: bool;
    mutable c_icanon: bool;
    mutable c_noflsh: bool;
    mutable c_echo: bool;
    mutable c_echoe: bool;
    mutable c_echok: bool;
    mutable c_echonl: bool;
    mutable c_vintr: char;
    mutable c_vquit: char;
    mutable c_verase: char;
    mutable c_vkill: char;
    mutable c_veof: char;
    mutable c_veol: char;
    mutable c_vmin: int;
    mutable c_vtime: int;
    mutable c_vstart: char;
    mutable c_vstop: char
  }

external tcgetattr: file_descr -> terminal_io = "unix_tcgetattr"

type setattr_when = TCSANOW | TCSADRAIN | TCSAFLUSH

external tcsetattr: file_descr -> setattr_when -> terminal_io -> unit
               = "unix_tcsetattr"
external tcsendbreak: file_descr -> int -> unit = "unix_tcsendbreak"
external tcdrain: file_descr -> unit = "unix_tcdrain"

type flush_queue = TCIFLUSH | TCOFLUSH | TCIOFLUSH

external tcflush: file_descr -> flush_queue -> unit = "unix_tcflush"

type flow_action = TCOOFF | TCOON | TCIOFF | TCION

external tcflow: file_descr -> flow_action -> unit = "unix_tcflow"

external setsid : unit -> int = "unix_setsid"

(* High-level process management (system, popen) *)

let system cmd =
  match fork() with
     0 -> begin try
            execv "/bin/sh" [| "/bin/sh"; "-c"; cmd |]
          with _ ->
            exit 127
          end
  | id -> snd(waitpid [] id)

let rec safe_dup fd =
  let new_fd = dup fd in
  if new_fd >= 3 then
    new_fd
  else begin
    let res = safe_dup fd in
    close new_fd;
    res
  end

let safe_close fd =
  try close fd with Unix_error(_,_,_) -> ()

let perform_redirections new_stdin new_stdout new_stderr =
  let newnewstdin = safe_dup new_stdin in
  let newnewstdout = safe_dup new_stdout in
  let newnewstderr = safe_dup new_stderr in
  safe_close new_stdin;
  safe_close new_stdout;
  safe_close new_stderr;
  dup2 newnewstdin stdin; close newnewstdin;
  dup2 newnewstdout stdout; close newnewstdout;
  dup2 newnewstderr stderr; close newnewstderr

let create_process cmd args new_stdin new_stdout new_stderr =
  match fork() with
    0 ->
      begin try
        perform_redirections new_stdin new_stdout new_stderr;
        execvp cmd args
      with _ ->
        exit 127
      end
  | id -> id

let create_process_env cmd args env new_stdin new_stdout new_stderr =
  match fork() with
    0 ->
      begin try
        perform_redirections new_stdin new_stdout new_stderr;
        execvpe cmd args env
      with _ ->
        exit 127
      end
  | id -> id

type popen_process =
    Process of in_channel * out_channel
  | Process_in of in_channel
  | Process_out of out_channel
  | Process_full of in_channel * out_channel * in_channel

let popen_processes = (Hashtbl.create 7 : (popen_process, int) Hashtbl.t)

let open_proc cmd proc input output toclose =
  match fork() with
     0 -> if input <> stdin then begin dup2 input stdin; close input end;
          if output <> stdout then begin dup2 output stdout; close output end;
          List.iter close toclose;
          execv "/bin/sh" [| "/bin/sh"; "-c"; cmd |];
          exit 127
  | id -> Hashtbl.add popen_processes proc id

let open_process_in cmd =
  let (in_read, in_write) = pipe() in
  let inchan = in_channel_of_descr in_read in
  open_proc cmd (Process_in inchan) stdin in_write [in_read];
  close in_write;
  inchan

let open_process_out cmd =
  let (out_read, out_write) = pipe() in
  let outchan = out_channel_of_descr out_write in
  open_proc cmd (Process_out outchan) out_read stdout [out_write];
  close out_read;
  outchan

let open_process cmd =
  let (in_read, in_write) = pipe() in
  let (out_read, out_write) = pipe() in
  let inchan = in_channel_of_descr in_read in
  let outchan = out_channel_of_descr out_write in
  open_proc cmd (Process(inchan, outchan)) out_read in_write
                                           [in_read; out_write];
  close out_read;
  close in_write;
  (inchan, outchan)

let open_proc_full cmd env proc input output error toclose =
  match fork() with
     0 -> dup2 input stdin; close input;
          dup2 output stdout; close output;
          dup2 error stderr; close error;
          List.iter close toclose;
          execve "/bin/sh" [| "/bin/sh"; "-c"; cmd |] env;
          exit 127
  | id -> Hashtbl.add popen_processes proc id

let open_process_full cmd env =
  let (in_read, in_write) = pipe() in
  let (out_read, out_write) = pipe() in
  let (err_read, err_write) = pipe() in
  let inchan = in_channel_of_descr in_read in
  let outchan = out_channel_of_descr out_write in
  let errchan = in_channel_of_descr err_read in
  open_proc_full cmd env (Process_full(inchan, outchan, errchan))
                 out_read in_write err_write [in_read; out_write; err_read];
  close out_read;
  close in_write;
  close err_write;
  (inchan, outchan, errchan)

let find_proc_id fun_name proc =
  try
    let pid = Hashtbl.find popen_processes proc in
    Hashtbl.remove popen_processes proc;
    pid
  with Not_found ->
    raise(Unix_error(EBADF, fun_name, ""))

let close_process_in inchan =
  let pid = find_proc_id "close_process_in" (Process_in inchan) in
  close_in inchan;
  snd(waitpid [] pid)

let close_process_out outchan =
  let pid = find_proc_id "close_process_out" (Process_out outchan) in
  close_out outchan;
  snd(waitpid [] pid)

let close_process (inchan, outchan) =
  let pid = find_proc_id "close_process" (Process(inchan, outchan)) in
  close_in inchan;
  begin try close_out outchan with Sys_error _ -> () end;
  snd(waitpid [] pid)

let close_process_full (inchan, outchan, errchan) =
  let pid =
    find_proc_id "close_process_full"
                 (Process_full(inchan, outchan, errchan)) in
  close_in inchan;
  begin try close_out outchan with Sys_error _ -> () end;
  close_in errchan;
  snd(waitpid [] pid)

(* High-level network functions *)

let open_connection sockaddr =
  let domain =
    match sockaddr with ADDR_UNIX _ -> PF_UNIX | ADDR_INET(_,_) -> PF_INET in
  let sock =
    socket domain SOCK_STREAM 0 in
  try
    connect sock sockaddr;
    (in_channel_of_descr sock, out_channel_of_descr sock)
  with exn ->
    close sock; raise exn

let shutdown_connection inchan =
  shutdown (descr_of_in_channel inchan) SHUTDOWN_SEND

let establish_server server_fun sockaddr =
  let domain =
    match sockaddr with ADDR_UNIX _ -> PF_UNIX | ADDR_INET(_,_) -> PF_INET in
  let sock =
    socket domain SOCK_STREAM 0 in
  setsockopt sock SO_REUSEADDR true;
  bind sock sockaddr;
  listen sock 5;
  while true do
    let (s, caller) = accept sock in
    (* The "double fork" trick, the process which calls server_fun will not
       leave a zombie process *)
    match fork() with
       0 -> if fork() <> 0 then exit 0; (* The son exits, the grandson works *)
            let inchan = in_channel_of_descr s in
            let outchan = out_channel_of_descr s in
            server_fun inchan outchan;
            close_out outchan;
            (* The file descriptor was already closed by close_out.
               close_in inchan;
            *)
            exit 0
    | id -> close s; ignore(waitpid [] id) (* Reclaim the son *)
  done