lwt_unix.cppo.mli

(* This file is part of Lwt, released under the MIT license. See LICENSE.md for
   details, or visit https://github.com/ocsigen/lwt/blob/master/LICENSE.md. *)



(** Cooperative system calls *)

(** This modules maps system calls, like those of the standard
    library's [Unix] module, to cooperative ones, which will not block
    the program.

    The semantics of all operations is the following: if the action
    (for example reading from a {b file descriptor}) can be performed
    immediately, it is performed and returns an already resolved promise,
    otherwise it returns a pending promise which is resolved when the operation
    completes.

    Most operations on sockets and pipes (on Windows it is only
    sockets) are {b cancelable}, meaning you can cancel them
    with {!Lwt.cancel}. For example if you want to read something from
    a {b file descriptor} with a timeout, you can cancel the action
    after the timeout and the reading will not be performed if not
    already done.

    For example, consider that you have two sockets [sock1] and
    [sock2]. You want to read something from [sock1] or exclusively
    from [sock2] and fail with an exception if a timeout of 1 second
    expires, without reading anything from [sock1] and [sock2], even
    if they become readable in the future.

    Then you can do:

    {[
    Lwt.pick
      [Lwt_unix.timeout 1.0;
       read sock1 buf1 ofs1 len1;
       read sock2 buf2 ofs2 len2]
    ]}

    In this case, it is guaranteed that exactly one of the three
    operations will complete, and the others will be cancelled.
*)

val handle_unix_error : ('a -> 'b Lwt.t) -> 'a -> 'b Lwt.t
  (** Same as [Unix.handle_unix_error] but catches lwt-level
      exceptions *)

(** {2 Sleeping} *)

val sleep : float -> unit Lwt.t
  (** [sleep d] is a promise that remains in a pending state for [d] seconds
      and after which it is resolved with value [()]. *)

val yield : unit -> unit Lwt.t
  (** [yield ()] is a promise in a pending state. It resumes itself as soon as
      possible and resolves with value [()]. *)

val auto_yield : float -> (unit -> unit Lwt.t)
  (** [auto_yield timeout] returns a function [f], and [f ()] has the following
      behavior:

      - If it has been more than [timeout] seconds since the last time [f ()]
        behaved like {!Lwt_unix.yield}, [f ()] calls {!Lwt_unix.yield}.
      - Otherwise, if it has been less than [timeout] seconds, [f ()] behaves
        like {!Lwt.return_unit}, i.e. it does not yield. *)

exception Timeout
  (** Exception raised by timeout operations *)

val timeout : float -> 'a Lwt.t
  (** [timeout d] is a promise that remains pending for [d] seconds
      and then is rejected with {!Timeout}. *)

val with_timeout : float -> (unit -> 'a Lwt.t) -> 'a Lwt.t
  (** [with_timeout d f] is a short-hand for:

      {[
        Lwt.pick [Lwt_unix.timeout d; f ()]
      ]}
  *)

(** {2 Operation on file-descriptors} *)

type file_descr
  (** The abstract type for {b file descriptor}s. A Lwt {b file
      descriptor} is a pair of a unix {b file descriptor} (of type
      [Unix.file_descr]) and a {b state}.

      A {b file descriptor} may be:

      - {b opened}, in which case it is fully usable
      - {b closed} or {b aborted}, in which case it is no longer
      usable *)

(** State of a {b file descriptor} *)
type state =
  | Opened
      (** The {b file descriptor} is opened *)
  | Closed
      (** The {b file descriptor} has been closed by {!close}. It must
          not be used for any operation. *)
  | Aborted of exn
      (** The {b file descriptor} has been aborted, the only operation
          possible is {!close}, all others will fail. *)

val state : file_descr -> state
  (** [state fd] returns the state of [fd] *)

val unix_file_descr : file_descr -> Unix.file_descr
  (** Returns the underlying unix {b file descriptor}. It always
      succeeds, even if the {b file descriptor}'s state is not
      [Open]. *)

val of_unix_file_descr : ?blocking : bool -> ?set_flags : bool -> Unix.file_descr -> file_descr
(** Wraps a [Unix] file descriptor [fd] in an [Lwt_unix.file_descr] [fd'].

    [~blocking] controls the {e internal} strategy Lwt uses to perform I/O on
    the underlying [fd]. Regardless of [~blocking], at the API level,
    [Lwt_unix.read], [Lwt_unix.write], etc. on [fd'] {e always} block the Lwt
    thread, but {e never} block the whole process. However, for performance
    reasons, it is important that [~blocking] match the actual blocking mode of
    [fd].

    If [~blocking] is not specified, [of_unix_file_descr] chooses non-blocking
    mode for Unix sockets, Unix pipes, and Windows sockets, and blocking mode
    for everything else. {b Note:} not specifying [~blocking] causes [fstat] to
    be lazily called on [fd], the first time your code performs I/O on [fd'].
    This [fstat] call can be expensive, so if you use [of_unix_file_descr] a
    lot, be sure to specify [~blocking] explicitly.

    [of_unix_file_descr] runs a system call to set the specified or chosen
    blocking mode on the underlying [fd].

    To prevent [of_unix_file_descr] from running this system call, you can pass
    [~set_flags:false]. Note that, in this case, if [~blocking], whether passed
    explicitly or chosen by Lwt, does not match the true blocking mode of the
    underlying [fd], I/O on [fd'] will suffer performance degradation.

    Note that [~set_flags] is effectively always [false] if running on Windows
    and [fd] is not a socket.

    Generally, non-blocking I/O is faster: for blocking I/O, Lwt typically has
    to run system calls in worker threads to avoid blocking the process. See
    your system documentation for whether particular kinds of file descriptors
    support non-blocking I/O. *)

val blocking : file_descr -> bool Lwt.t
(** [blocking fd] indicates whether Lwt is internally using blocking or
    non-blocking I/O with [fd].

    Note that this may differ from the blocking mode of the underlying [Unix]
    file descriptor (i.e. [unix_file_descr fd]).

    See {!of_unix_file_descr} for details. *)

val set_blocking : ?set_flags : bool -> file_descr -> bool -> unit
(** [set_blocking fd b] causes Lwt to internally use blocking or non-blocking
    I/O with [fd], according to the value of [b].

    If [~set_flags] is [true] (the default), Lwt also makes a system call to set
    the underlying file descriptor's blocking mode to match. Otherwise,
    [set_blocking] is only informational for Lwt.

    It is important that the underlying file descriptor actually have the same
    blocking mode as that indicated by [b].

    See {!of_unix_file_descr} for details. *)

val abort : file_descr -> exn -> unit
  (** [abort fd exn] makes all current and further uses of the file
      descriptor fail with the given exception. This put the {b file
      descriptor} into the [Aborted] state.

      If the {b file descriptor} is closed, this does nothing, if it is
      aborted, this replace the abort exception by [exn].

      Note that this only works for reading and writing operations on
      file descriptors supporting non-blocking mode. *)

(** {2 Process handling} *)

val fork : unit -> int
  (** [fork ()] does the same as [Unix.fork]. You must use this
      function instead of [Unix.fork] when you want to use Lwt in the
      child process.

      Notes:

      - In the child process all pending [Lwt_unix] I/O jobs are abandoned.
        This may cause the child's copy of their associated promises to remain
        forever pending.
      - If you are going to use Lwt in the parent and the child, it is
        a good idea to call {!Lwt_io.flush_all} before callling
        {!fork} to avoid double-flush.
      - Otherwise, if you will not use Lwt in the child, call
        {!Lwt_main.Exit_hooks.remove_all} to avoid Lwt calling {!Lwt_main.run}
        during process exit.
      - None of the above is necessary if you intend to call [exec]. Indeed, in
        that case, it is not even necessary to use [Lwt_unix.fork]. You can use
        [Unix.fork].
      - To abandon some more promises, see
        {!Lwt_main.abandon_yielded_and_paused}. *)

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

type wait_flag =
    Unix.wait_flag =
  | WNOHANG
  | WUNTRACED

val wait : unit -> (int * process_status) Lwt.t
  (** Wrapper for [Unix.wait] *)

val waitpid : wait_flag list -> int -> (int * process_status) Lwt.t
(** A promise-returning analog to
    {{: https://caml.inria.fr/pub/docs/manual-ocaml/libref/Unix.html#VALwaitpid}
    [Unix.waitpid]}. This call is non-blocking on Unix-like systems, but is
    always blocking on Windows. *)

(** Resource usages *)
type resource_usage = {
  ru_utime : float;
  (** User time used *)

  ru_stime : float;
  (** System time used *)
}

val wait4 : wait_flag list -> int -> (int * process_status * resource_usage) Lwt.t
  (** [wait4 flags pid] returns [(pid, status, rusage)] where [(pid, status)]
      is the same result as [Unix.waitpid flags pid], and
      [rusage] contains accounting information about the child.

      On windows it will always returns [{ utime = 0.0; stime = 0.0 }]. *)

val wait_count : unit -> int
  (** Returns the number of threads waiting for a child to
      terminate. *)

val system : string -> process_status Lwt.t
  (** Executes the given command, waits until it terminates, and
      return its termination status. The string is interpreted by the
      shell [/bin/sh] on Unix and [cmd.exe] on Windows. The result
      [WEXITED 127] indicates that the shell couldn't be executed. *)

(** {2 Basic file input/output} *)

val stdin : file_descr
  (** The standard {b file descriptor} for input. This one is usually
      a terminal is the program is started from a terminal. *)

val stdout : file_descr
  (** The standard {b file descriptor} for output *)

val stderr : file_descr
  (** The standard {b file descriptor} for printing error messages *)

type file_perm = Unix.file_perm

type open_flag =
    Unix.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
  | O_SHARE_DELETE
  | O_CLOEXEC
#if OCAML_VERSION >= (4, 05, 0)
  | O_KEEPEXEC
#endif

val openfile : string -> open_flag list -> file_perm -> file_descr Lwt.t
  (** Wrapper for [Unix.openfile]. *)

val close : file_descr -> unit Lwt.t
  (** Close a {b file descriptor}. This close the underlying unix {b
      file descriptor} and set its state to [Closed]. *)

val read : file_descr -> bytes -> int -> int -> int Lwt.t
(** [read fd buf ofs len] reads up to [len] bytes from [fd], and writes them to
    [buf], starting at offset [ofs]. The function immediately evaluates to an
    Lwt thread, which waits for the operation to complete. If it completes
    successfully, the thread indicates the number of bytes actually read, or
    zero if the end of file has been reached.

    Note that the Lwt thread waits for data (or end of file) even if the
    underlying file descriptor is in non-blocking mode. See
    {!of_unix_file_descr} for a discussion of non-blocking I/O and Lwt.

    If Lwt is using blocking I/O on [fd], [read] writes data into a temporary
    buffer, then copies it into [buf].

    The thread can fail with any exception that can be raised by [Unix.read],
    except [Unix.Unix_error Unix.EAGAIN], [Unix.Unix_error Unix.EWOULDBLOCK] or
    [Unix.Unix_error Unix.EINTR]. *)

val pread : file_descr -> bytes -> file_offset:int -> int -> int -> int Lwt.t
(** [pread fd buf ~file_offset ofs len] on file descriptors allowing seek,
    reads up to [len] bytes from [fd] at offset [file_offset] from the
    beginning of the file, and writes them to [buf], starting at offset [ofs].

    On Unix systems, the file descriptor position is unaffected. On Windows
    it is changed to be just after the last read position.

    The thread can fail with any exception that can be raised by [read] or
    [lseek]. *)

val write : file_descr -> bytes -> int -> int -> int Lwt.t
(** [write fd buf ofs len] writes up to [len] bytes to [fd] from [buf], starting
    at buffer offset [ofs]. The function immediately evaluates to an Lwt thread,
    which waits for the operation to complete. If the operation completes
    successfully, the thread indicates the number of bytes actually written,
    which may be less than [len].

    Note that the Lwt thread waits to write even if the underlying file
    descriptor is in non-blocking mode. See {!of_unix_file_descr} for a
    discussion of non-blocking I/O and Lwt.

    If Lwt is using blocking I/O on [fd], [buf] is copied before writing.

    The thread can fail with any exception that can be raised by
    [Unix.single_write], except [Unix.Unix_error Unix.EAGAIN],
    [Unix.Unix_error Unix.EWOULDBLOCK] or [Unix.Unix_error Unix.EINTR]. *)

val pwrite : file_descr -> bytes -> file_offset:int -> int -> int -> int Lwt.t
(** [pwrite fd buf ~file_offset ofs len] on file descriptors allowing seek,
    writes up to [len] bytes to [fd] from [buf], starting at buffer offset
    [ofs]. The data is written at offset [file_offset] from the beginning
    of [fd].

    On Unix systems, the file descriptor position is unaffected. On Windows
    it is changed to be just after the last written position.

    The thread can fail with any exception that can be raised by [write] or
    [lseek]. *)

val write_string : file_descr -> string -> int -> int -> int Lwt.t
  (** See {!write}. *)

val pwrite_string :
  file_descr -> string -> file_offset:int -> int -> int -> int Lwt.t
  (** See {!pwrite}. *)

(** Sequences of buffer slices for {!writev}. *)
module IO_vectors :
sig
  type t
  (** Mutable sequences of I/O vectors. An I/O vector describes a slice of a
      [bytes] or [Bigarray] buffer. Each I/O vector is a triple containing a
      reference to the buffer, an offset into the buffer where the slice begins,
      and the length of the slice. *)

  type _bigarray =
    (char, Bigarray.int8_unsigned_elt, Bigarray.c_layout) Bigarray.Array1.t
  (** Type abbreviation equivalent to {!Lwt_bytes.t}. Do not use this type name
      directly; use {!Lwt_bytes.t} instead. *)

  val create : unit -> t
  (** Creates an empty I/O vector sequence. *)

  val append_bytes : t -> bytes -> int -> int -> unit
  (** [append_bytes vs buffer offset length] appends a slice of the [bytes]
      buffer [buffer] beginning at [offset] and with length [length] to the
      I/O vector sequence [vs]. *)

  val append_bigarray : t -> _bigarray -> int -> int -> unit
  (** [append_bigarray vs buffer offset length] appends a slice of the
      [Bigarray] buffer [buffer] beginning at [offset] and with length [length]
      to the I/O vector sequence [vs]. *)

  val drop : t -> int -> unit
  (** [drop vs n] adjusts the I/O vector sequence [vs] so that it no longer
      includes its first [n] bytes. *)

  val is_empty : t -> bool
  (** [is_empty vs] is [true] if and only if [vs] has no I/O vectors, or all I/O
      vectors in [vs] have zero bytes. *)

  val byte_count : t -> int
  (** [byte_count vs] is the total number of bytes in [vs].

      @since 4.2.0 *)

  val system_limit : int option
  (** Some systems limit the number of I/O vectors that can be passed in a
      single call to their [writev] or [readv] system calls. On those systems,
      if the limit is [n], this value is equal to [Some n]. On systems without
      such a limit, the value is equal to [None].

      Unless you need atomic I/O operations, you can ignore this limit. The Lwt
      binding automatically respects it internally. See {!Lwt_unix.writev}.

      A typical limit is 1024 vectors. *)
end

val readv : file_descr -> IO_vectors.t -> int Lwt.t
(** [readv fd vs] reads bytes from [fd] into the buffer slices [vs]. If the
    operation completes successfully, the resulting thread indicates the number
    of bytes read.

    Data is always read directly into [Bigarray] slices. If the Unix file
    descriptor underlying [fd] is in non-blocking mode, data is also read
    directly into [bytes] slices. Otherwise, data for [bytes] slices is first
    read into temporary buffers, then copied.

    Note that the returned Lwt thread is blocked until failure or a successful
    read, even if the underlying file descriptor is in non-blocking mode. See
    {!of_unix_file_descr} for a discussion of non-blocking I/O and Lwt.

    If {!IO_vectors.system_limit} is [Some n] and the count of slices in [vs]
    exceeds [n], then [Lwt_unix.readv] reads only into the first [n] slices of
    [vs].

    Not implemented on Windows. It should be possible to implement, upon
    request, for Windows sockets only.

    See {{:http://man7.org/linux/man-pages/man3/readv.3p.html} [readv(3p)]}.

    @since 2.7.0 *)

val writev : file_descr -> IO_vectors.t -> int Lwt.t
(** [writev fd vs] writes the bytes in the buffer slices [vs] to the file
    descriptor [fd]. If the operation completes successfully, the resulting
    thread indicates the number of bytes written.

    If the Unix file descriptor underlying [fd] is in non-blocking mode,
    [writev] does not make a copy the bytes before writing. Otherwise, it copies
    [bytes] slices, but not [Bigarray] slices.

    Note that the returned Lwt thread is blocked until failure or a successful
    write, even if the underlying descriptor is in non-blocking mode. See
    {!of_unix_file_descr} for a discussion of non-blocking I/O and Lwt.

    If {!IO_vectors.system_limit} is [Some n] and the count of slices in [vs]
    exceeds [n], then [Lwt_unix.writev] passes only the first [n] slices in [vs]
    to the underlying [writev] system call.

    Not implemented on Windows. It should be possible to implement, upon
    request, for Windows sockets only.

    The behavior of [writev] when [vs] has zero slices depends on the system,
    and may change in future versions of Lwt. On Linux, [writev] will succeed
    and write zero bytes. On BSD (including macOS), [writev] will fail with
    [Unix.Unix_error (Unix.EINVAL, "writev", ...)].

    See {{:http://man7.org/linux/man-pages/man3/writev.3p.html}
    [writev(3p)]}.

    @since 2.7.0 *)

val readable : file_descr -> bool
  (** Returns whether the given file descriptor is currently
      readable. *)

val writable : file_descr -> bool
  (** Returns whether the given file descriptor is currently
      writable. *)

val wait_read : file_descr -> unit Lwt.t
  (** Waits (without blocking other threads) until there is something
      to read from the file descriptor.

      Note that you don't need to use this function if you are
      using Lwt I/O functions for reading, since they provide
      non-blocking waiting automatically.

      The intended use case for this function is interfacing with
      existing libraries that are known to be blocking. *)

val wait_write : file_descr -> unit Lwt.t
  (** Waits (without blocking other threads) until it is possible to
      write on the file descriptor.

      Note that you don't need to use this function if you are
      using Lwt I/O functions for writing, since they provide
      non-blocking waiting automatically.

      The intended use case for this function is interfacing with
      existing libraries that are known to be blocking. *)


(** {2 Seeking and truncating} *)

type seek_command =
    Unix.seek_command =
  | SEEK_SET
  | SEEK_CUR
  | SEEK_END

val lseek : file_descr -> int -> seek_command -> int Lwt.t
  (** Wrapper for [Unix.lseek] *)

val truncate : string -> int -> unit Lwt.t
  (** Wrapper for [Unix.truncate] *)

val ftruncate : file_descr -> int -> unit Lwt.t
  (** Wrapper for [Unix.ftruncate] *)

(** {2 Syncing} *)

val fsync : file_descr -> unit Lwt.t
  (** Synchronise all data and metadata of the file descriptor with
      the disk. On Windows it uses [FlushFileBuffers]. *)

val fdatasync : file_descr -> unit Lwt.t
  (** Synchronise all data (but not metadata) of the file descriptor
      with the disk.

      Note that [fdatasync] is not available on Windows and OS X. *)

(** {2 File status} *)

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

type stats =
    Unix.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;
    }

val stat : string -> stats Lwt.t
  (** Wrapper for [Unix.stat] *)

val lstat : string -> stats Lwt.t
  (** Wrapper for [Unix.lstat] *)

val fstat : file_descr -> stats Lwt.t
  (** Wrapper for [Unix.fstat] *)

val file_exists : string -> bool Lwt.t
  (** [file_exists name] tests if a file named [name] exists.

      Note that [file_exists] behaves similarly to
      {{:http://caml.inria.fr/pub/docs/manual-ocaml/libref/Sys.html#VALfile_exists}
      [Sys.file_exists]}:

      - "file" is interpreted as "directory entry" in this context

      - [file_exists name] will return [false] in
        circumstances that would make {!stat} raise a
        {{:http://caml.inria.fr/pub/docs/manual-ocaml/libref/Unix.html#EXCEPTIONUnix_error}
        [Unix.Unix_error]} exception.
     *)

val utimes : string -> float -> float -> unit Lwt.t
(** [utimes path atime mtime] updates the access and modification times of the
    file at [path]. The access time is set to [atime] and the modification time
    to [mtime]. To set both to the current time, call [utimes path 0. 0.].

    This function corresponds to
    {{:http://caml.inria.fr/pub/docs/manual-ocaml/libref/Unix.html#VALutimes}
    [Unix.utimes]}. See also
    {{:http://man7.org/linux/man-pages/man3/utimes.3p.html} [utimes(3p)]}.

    @since 2.6.0 *)

val isatty : file_descr -> bool Lwt.t
  (** Wrapper for [Unix.isatty] *)

(** {2 File operations on large files} *)

module LargeFile : sig
  val lseek : file_descr -> int64 -> seek_command -> int64 Lwt.t
    (** Wrapper for [Unix.LargeFile.lseek] *)

  val truncate : string -> int64 -> unit Lwt.t
    (** Wrapper for [Unix.LargeFile.truncate] *)

  val ftruncate : file_descr -> int64 -> unit Lwt.t
    (** Wrapper for [Unix.LargeFile.ftruncate] *)

  type stats =
      Unix.LargeFile.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;
      }

  val stat : string -> stats Lwt.t
    (** Wrapper for [Unix.LargeFile.stat] *)

  val lstat : string -> stats Lwt.t
    (** Wrapper for [Unix.LargeFile.lstat] *)

  val fstat : file_descr -> stats Lwt.t
    (** Wrapper for [Unix.LargeFile.fstat] *)

  val file_exists : string -> bool Lwt.t
    (** [file_exists name] tests if a file named [name] exists.

        Note that [file_exists] behaves similarly to
        {{:http://caml.inria.fr/pub/docs/manual-ocaml/libref/Sys.html#VALfile_exists}
        [Sys.file_exists]}:

        - "file" is interpreted as "directory entry" in this context

        - [file_exists name] will return [false] in
          circumstances that would make {!stat} raise a
          {{:http://caml.inria.fr/pub/docs/manual-ocaml/libref/Unix.html#EXCEPTIONUnix_error}
          [Unix.Unix_error]} exception.
     *)
end

(** {2 Operations on file names} *)

val unlink : string -> unit Lwt.t
  (** Wrapper for [Unix.unlink] *)

val rename : string -> string -> unit Lwt.t
  (** Wrapper for [Unix.rename] *)

val link : string -> string -> unit Lwt.t
  (** Wrapper for [Unix.link] *)

(** {2 File permissions and ownership} *)

val chmod : string -> file_perm -> unit Lwt.t
  (** Wrapper for [Unix.chmod] *)

val fchmod : file_descr -> file_perm -> unit Lwt.t
  (** Wrapper for [Unix.fchmod] *)

val chown : string -> int -> int -> unit Lwt.t
  (** Wrapper for [Unix.chown] *)

val fchown : file_descr -> int -> int -> unit Lwt.t
  (** Wrapper for [Unix.fchown] *)

type access_permission =
    Unix.access_permission =
  | R_OK
  | W_OK
  | X_OK
  | F_OK

val access : string -> access_permission list -> unit Lwt.t
  (** Wrapper for [Unix.access] *)

(** {2 Operations on file descriptors} *)

val dup : file_descr -> file_descr
  (** Wrapper for [Unix.dup] *)

val dup2 : file_descr -> file_descr -> unit
  (** Wrapper for [Unix.dup2] *)

val set_close_on_exec : file_descr -> unit
  (** Wrapper for [Unix.set_close_on_exec] *)

val clear_close_on_exec : file_descr -> unit
  (** Wrapper for [Unix.clear_close_on_exec] *)

(** {2 Directories} *)

val mkdir : string -> file_perm -> unit Lwt.t
  (** Wrapper for [Unix.mkdir] *)

val rmdir : string -> unit Lwt.t
  (** Wrapper for [Unix.rmdir] *)

val chdir : string -> unit Lwt.t
  (** Wrapper for [Unix.chdir] *)

val getcwd : unit -> string Lwt.t
(** Wrapper for [Unix.getcwd]

    @since 3.1.0 *)

val chroot : string -> unit Lwt.t
  (** Wrapper for [Unix.chroot] *)

type dir_handle = Unix.dir_handle

val opendir : string -> dir_handle Lwt.t
(** Opens a directory for listing. Directories opened with this function must be
    explicitly closed with {!closedir}. This is a cooperative analog of
    {{:http://caml.inria.fr/pub/docs/manual-ocaml/libref/Unix.html#VALopendir}
    [Unix.opendir]}. *)

val readdir : dir_handle -> string Lwt.t
(** Reads the next directory entry from the given directory. Special entries
    such as [.] and [..] are included. If all entries have been read, raises
    [End_of_file]. This is a cooperative analog of
    {{:http://caml.inria.fr/pub/docs/manual-ocaml/libref/Unix.html#VALreaddir}
    [Unix.readdir]}. *)

val readdir_n : dir_handle -> int -> string array Lwt.t
  (** [readdir_n handle count] reads at most [count] entries from the
      given directory. It is more efficient than calling [readdir]
      [count] times. If the length of the returned array is smaller
      than [count], this means that the end of the directory has been
      reached. *)

val rewinddir : dir_handle -> unit Lwt.t
(** Resets the given directory handle, so that directory listing can be
    restarted. Cooperative analog of
    {{:http://caml.inria.fr/pub/docs/manual-ocaml/libref/Unix.html#VALrewinddir}
    [Unix.rewinddir]}. *)

val closedir : dir_handle -> unit Lwt.t
(** Closes a directory handle. Cooperative analog of
    {{:http://caml.inria.fr/pub/docs/manual-ocaml/libref/Unix.html#VALclosedir}
    [Unix.closedir]}. *)

val files_of_directory : string -> string Lwt_stream.t
  (** [files_of_directory dir] returns the stream of all files of
      [dir]. *)

(** {2 Pipes and redirections} *)

val pipe : unit -> file_descr * file_descr
  (** [pipe ()] creates pipe using [Unix.pipe] and returns two lwt {b
      file descriptor}s created from unix {b file_descriptor} *)

val pipe_in : unit -> file_descr * Unix.file_descr
  (** [pipe_in ()] is the same as {!pipe} but maps only the unix {b
      file descriptor} for reading into a lwt one. The second is not
      put into non-blocking mode. You usually want to use this before
      forking to receive data from the child process. *)

val pipe_out : unit -> Unix.file_descr * file_descr
  (** [pipe_out ()] is the inverse of {!pipe_in}. You usually want to
      use this before forking to send data to the child process *)

val mkfifo : string -> file_perm -> unit Lwt.t
  (** Wrapper for [Unix.mkfifo] *)

(** {2 Symbolic links} *)

val symlink : string -> string -> unit Lwt.t
  (** Wrapper for [Unix.symlink] *)

val readlink : string -> string Lwt.t
  (** Wrapper for [Unix.readlink] *)

(** {2 Locking} *)

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

val lockf : file_descr -> lock_command -> int -> unit Lwt.t
  (** Wrapper for [Unix.lockf] *)

(** {2 User id, group id} *)

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

val getlogin : unit -> string Lwt.t
  (** Wrapper for [Unix.getlogin] *)

val getpwnam : string -> passwd_entry Lwt.t
  (** Wrapper for [Unix.getpwnam] *)

val getgrnam : string -> group_entry Lwt.t
  (** Wrapper for [Unix.getgrnam] *)

val getpwuid : int -> passwd_entry Lwt.t
  (** Wrapper for [Unix.getpwuid] *)

val getgrgid : int -> group_entry Lwt.t
  (** Wrapper for [Unix.getgrgid] *)

(** {2 Signals} *)

type signal_handler_id
  (** Id of a signal handler, used to cancel it *)

val on_signal : int -> (int -> unit) -> signal_handler_id
  (** [on_signal signum f] calls [f] each time the signal with numnber
      [signum] is received by the process. It returns a signal handler
      identifier that can be used to stop monitoring [signum]. *)

val on_signal_full : int -> (signal_handler_id -> int -> unit) -> signal_handler_id
  (** [on_signal_full f] is the same as [on_signal f] except that [f]
      also receive the signal handler identifier as argument so it can
      disable it. *)

val disable_signal_handler : signal_handler_id -> unit
  (** Stops receiving this signal *)

val signal_count : unit -> int
  (** Returns the number of registered signal handler. *)

val reinstall_signal_handler : int -> unit
  (** [reinstall_signal_handler signum] if any signal handler is
      registered for this signal with {!on_signal}, it reinstall the
      signal handler (with [Sys.set_signal]). This is useful in case
      another part of the program install another signal handler. *)

(** {2 Sockets} *)

type inet_addr = Unix.inet_addr

type socket_domain =
    Unix.socket_domain =
  | PF_UNIX
  | PF_INET
  | PF_INET6

type socket_type =
    Unix.socket_type =
  | SOCK_STREAM
  | SOCK_DGRAM
  | SOCK_RAW
  | SOCK_SEQPACKET

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

val socket : socket_domain -> socket_type -> int -> file_descr
  (** [socket domain type proto] is the same as [Unix.socket] but maps
      the result into a lwt {b file descriptor} *)

val socketpair : socket_domain -> socket_type -> int -> file_descr * file_descr
  (** Wrapper for [Unix.socketpair] *)

val bind : file_descr -> sockaddr -> unit Lwt.t
(** Binds an address to the given socket. This is the cooperative analog of
    {{:http://caml.inria.fr/pub/docs/manual-ocaml/libref/Unix.html#VALbind}
    [Unix.bind]}. See also
    {{:http://man7.org/linux/man-pages/man3/bind.3p.html} [bind(3p)]}.

    @since 3.0.0 *)

val listen : file_descr -> int -> unit
  (** Wrapper for [Unix.listen] *)

val accept : file_descr -> (file_descr * sockaddr) Lwt.t
  (** Wrapper for [Unix.accept] *)

val accept_n : file_descr -> int -> ((file_descr * sockaddr) list * exn option) Lwt.t
  (** [accept_n fd count] accepts up to [count] connections at one time.

      - if no connection is available right now, it returns a sleeping
      thread

      - if more than 1 and less than [count] are available, it returns
      all of them

      - if more than [count] are available, it returns the next
      [count] of them

      - if an error happens, it returns the connections that have been
      successfully accepted so far and the error

      [accept_n] has the advantage of improving performance. If you
      want a more detailed description, you can have a look at:

      {{:http://portal.acm.org/citation.cfm?id=1247435}Acceptable strategies for improving web server performance} *)

val connect : file_descr -> sockaddr -> unit Lwt.t
  (** Wrapper for [Unix.connect] *)

type shutdown_command =
    Unix.shutdown_command =
  | SHUTDOWN_RECEIVE
  | SHUTDOWN_SEND
  | SHUTDOWN_ALL

val shutdown : file_descr -> shutdown_command -> unit
  (** Wrapper for [Unix.shutdown] *)

val getsockname : file_descr -> sockaddr
  (** Wrapper for [Unix.getsockname] *)

val getpeername : file_descr -> sockaddr
  (** Wrapper for [Unix.getpeername] *)

type msg_flag =
    Unix.msg_flag =
  | MSG_OOB
  | MSG_DONTROUTE
  | MSG_PEEK

val recv : file_descr -> bytes -> int -> int -> msg_flag list -> int Lwt.t
(** Wrapper for [Unix.recv].

    On Windows, [recv] writes data into a temporary buffer, then copies it into
    the given one. *)

val recvfrom : file_descr -> bytes -> int -> int -> msg_flag list -> (int * sockaddr) Lwt.t
(** Wrapper for [Unix.recvfrom].

    On Windows, [recvfrom] writes data into a temporary buffer, then copies it
    into the given one. *)

val send : file_descr -> bytes -> int -> int -> msg_flag list -> int Lwt.t
(** Wrapper for [Unix.send].

    On Windows, [send] copies the given buffer before writing. *)

val sendto : file_descr -> bytes -> int -> int -> msg_flag list -> sockaddr -> int Lwt.t
(** Wrapper for [Unix.sendto].

    On Windows, [sendto] copies the given buffer before writing. *)

val recv_msg :
  socket:file_descr -> io_vectors:IO_vectors.t ->
    (int * Unix.file_descr list) Lwt.t
(** [recv_msg ~socket ~io_vectors] receives data into a list of
    io-vectors, plus any file-descriptors that may accompany the
    messages. It returns a tuple whose first field is the number of
    bytes received and second is a list of received file
    descriptors. The messages themselves will be recorded in the
    provided [io_vectors] list. Data is written directly into the
    [iov_buffer] buffers.

    Not implemented on Windows.

    @since 5.0.0 *)

val send_msg :
  socket:file_descr -> io_vectors:IO_vectors.t -> fds:Unix.file_descr list ->
    int Lwt.t
(** [send_msg ~socket ~io_vectors ~fds] sends data from a list of
    io-vectors, accompanied with a list of file-descriptors. It
    returns the number of bytes sent. If fd-passing is not possible on
    the current system and [fds] is not empty, it raises
    [Lwt_sys.Not_available "fd_passing"]. Data is written directly from
    the [io_vectors] buffers.

    Not implemented on Windows.

    @since 5.0.0 *)

val send_msgto :
  socket:file_descr -> io_vectors:IO_vectors.t -> fds:Unix.file_descr list ->
    dest:Unix.sockaddr ->
    int Lwt.t
(** [send_msgto ~socket ~io_vectors ~fds ~dest] is similar to [send_msg] but
    takes an additional [dest] argument to set the address when using a
    connection-less socket.

    Not implemented on Windows.

    @since 5.4.0 *)

type credentials = {
  cred_pid : int;
  cred_uid : int;
  cred_gid : int;
}

val get_credentials : file_descr -> credentials
  (** [get_credentials fd] returns credentials information from the
      given socket. On some platforms, obtaining the peer pid is not
      possible and it will be set to [-1]. If obtaining credentials
      is not possible on the current system, it raises
      [Lwt_sys.Not_available "get_credentials"].

      This call is not available on windows. *)

(** {3 Socket options} *)

type socket_bool_option =
    Unix.socket_bool_option =
  | SO_DEBUG
  | SO_BROADCAST
  | SO_REUSEADDR
  | SO_KEEPALIVE
  | SO_DONTROUTE
  | SO_OOBINLINE
  | SO_ACCEPTCONN
  | TCP_NODELAY
  | IPV6_ONLY
#if OCAML_VERSION >= (4, 12, 0)
  | SO_REUSEPORT
#endif

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

type socket_optint_option = Unix.socket_optint_option = SO_LINGER

type socket_float_option =
    Unix.socket_float_option =
  | SO_RCVTIMEO
  | SO_SNDTIMEO
(** Note: these options are provided for the sake of completeness only. Lwt
    places all sockets in non-blocking mode, for which these options are
    meaningless. Use {!Lwt.pick} with {!Lwt_unix.sleep} or {!Lwt_unix.timeout}
    for timeouts. *)

val getsockopt : file_descr -> socket_bool_option -> bool
  (** Wrapper for [Unix.getsockopt] *)

val setsockopt : file_descr -> socket_bool_option -> bool -> unit
  (** Wrapper for [Unix.setsockopt] *)

val getsockopt_int : file_descr -> socket_int_option -> int
  (** Wrapper for [Unix.getsockopt_int] *)

val setsockopt_int : file_descr -> socket_int_option -> int -> unit
  (** Wrapper for [Unix.setsockopt_int] *)

val getsockopt_optint : file_descr -> socket_optint_option -> int option
  (** Wrapper for [Unix.getsockopt_optint] *)

val setsockopt_optint : file_descr -> socket_optint_option -> int option -> unit
  (** Wrapper for [Unix.setsockopt_optint] *)

val getsockopt_float : file_descr -> socket_float_option -> float
  (** Wrapper for [Unix.getsockopt_float] *)

val setsockopt_float : file_descr -> socket_float_option -> float -> unit
  (** Wrapper for [Unix.setsockopt_float] *)

val getsockopt_error : file_descr -> Unix.error option
  (** Wrapper for [Unix.getsockopt_error] *)

(** {3 Multicast functions} *)

val mcast_set_loop : file_descr -> bool -> unit
  (** Whether sent multicast messages are received by the sending host *)

val mcast_set_ttl : file_descr -> int -> unit
  (** Set TTL/hops value *)

val mcast_add_membership : file_descr -> ?ifname:Unix.inet_addr -> Unix.inet_addr -> unit
  (** [mcast_add_membership fd ~ifname addr] joins the multicast group [addr]
      on the network interface [ifname]. *)

val mcast_drop_membership : file_descr -> ?ifname:Unix.inet_addr -> Unix.inet_addr -> unit
  (** [mcast_drop_membership fd ~ifname addr] leaves the multicast group [addr]
      on the network interface [ifname]. *)

(** {2 Host and protocol databases} *)

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

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

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

val gethostname : unit -> string Lwt.t
  (** Wrapper for [Unix.gethostname] *)

val gethostbyname : string -> host_entry Lwt.t
  (** Wrapper for [Unix.gethostbyname] *)

val gethostbyaddr : inet_addr -> host_entry Lwt.t
  (** Wrapper for [Unix.gethostbyaddr] *)

val getprotobyname : string -> protocol_entry Lwt.t
  (** Wrapper for [Unix.getprotobyname] *)

val getprotobynumber : int -> protocol_entry Lwt.t
  (** Wrapper for [Unix.getprotobynumber] *)

val getservbyname : string -> string -> service_entry Lwt.t
  (** Wrapper for [Unix.getservbyname] *)

val getservbyport : int -> string -> service_entry Lwt.t
  (** Wrapper for [Unix.getservbyport] *)

type addr_info =
    Unix.addr_info =
    {
      ai_family : socket_domain;
      ai_socktype : socket_type;
      ai_protocol : int;
      ai_addr : sockaddr;
      ai_canonname : string;
    }

type getaddrinfo_option =
    Unix.getaddrinfo_option =
  | AI_FAMILY of socket_domain
  | AI_SOCKTYPE of socket_type
  | AI_PROTOCOL of int
  | AI_NUMERICHOST
  | AI_CANONNAME
  | AI_PASSIVE

val getaddrinfo : string -> string -> getaddrinfo_option list -> addr_info list Lwt.t
  (** Wrapper for [Unix.getaddrinfo] *)

type name_info =
    Unix.name_info =
    {
      ni_hostname : string;
      ni_service : string;
    }

type getnameinfo_option =
    Unix.getnameinfo_option =
  | NI_NOFQDN
  | NI_NUMERICHOST
  | NI_NAMEREQD
  | NI_NUMERICSERV
  | NI_DGRAM

val getnameinfo : sockaddr -> getnameinfo_option list -> name_info Lwt.t
  (** Wrapper for [Unix.getnameinfo] *)

(** {2 Terminal interface} *)

type terminal_io =
    Unix.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;
    }

val tcgetattr : file_descr -> terminal_io Lwt.t
  (** Wrapper for [Unix.tcgetattr] *)

type setattr_when =
    Unix.setattr_when =
  | TCSANOW
  | TCSADRAIN
  | TCSAFLUSH

val tcsetattr : file_descr -> setattr_when -> terminal_io -> unit Lwt.t
  (** Wrapper for [Unix.tcsetattr] *)

val tcsendbreak : file_descr -> int -> unit Lwt.t
  (** Wrapper for [Unix.tcsendbreak] *)

val tcdrain : file_descr -> unit Lwt.t
  (** Wrapper for [Unix.tcdrain] *)

type flush_queue =
    Unix.flush_queue =
  | TCIFLUSH
  | TCOFLUSH
  | TCIOFLUSH

val tcflush : file_descr -> flush_queue -> unit Lwt.t
  (** Wrapper for [Unix.tcflush] *)

type flow_action =
    Unix.flow_action =
  | TCOOFF
  | TCOON
  | TCIOFF
  | TCION

val tcflow : file_descr -> flow_action -> unit Lwt.t
  (** Wrapper for [Unix.tcflow] *)



(** {2 Configuration (deprecated)} *)

(** For system calls that cannot be made asynchronously, Lwt uses one
    of the following method: *)
type async_method =
  | Async_none
      (** System calls are made synchronously, and may block the
          entire program. *)
  | Async_detach
      (** System calls are made in another system thread, thus without
          blocking other Lwt threads. The drawback is that it may
          degrade performance in some cases.

          This is the default. *)
  | Async_switch
    [@ocaml.deprecated " Use Lwt_unix.Async_detach."]
      (** Currently a synonym for [Async_detach]. This was a different method in
          the past. *)

val default_async_method : unit -> async_method
  [@@ocaml.deprecated
" Will always return Async_detach in Lwt >= 5.0.0. See
   https://github.com/ocsigen/lwt/issues/572"]
(** Returns the default async method.

    This can be initialized using the environment variable
    ["LWT_ASYNC_METHOD"] with possible values ["none"],
    ["detach"] and ["switch"].

    @deprecated Will always return [Async_detach] in Lwt 5.0.0. *)

val set_default_async_method : async_method -> unit
  [@@ocaml.deprecated
" Will be a no-op in Lwt >= 5.0.0. See
   https://github.com/ocsigen/lwt/issues/572"]
(** Sets the default async method.

    @deprecated Will be a no-op in Lwt 5.0.0. *)

val async_method : unit -> async_method
  [@@ocaml.deprecated
" Will always return Async_detach in Lwt >= 5.0.0. See
   https://github.com/ocsigen/lwt/issues/572"]
(** [async_method ()] returns the async method used in the current
    thread.

    @deprecated Will always return [Async_detach] in Lwt 5.0.0. *)

val async_method_key : async_method Lwt.key
  [@@ocaml.deprecated
" Will be ignored in Lwt >= 5.0.0. See
   https://github.com/ocsigen/lwt/issues/572"]
(** The key for storing the local async method.

    @deprecated Will be ignored in Lwt 5.0.0. *)

val with_async_none : (unit -> 'a) -> 'a
  [@@ocaml.deprecated
" Will have no effect in Lwt >= 5.0.0. See
   https://github.com/ocsigen/lwt/issues/572"]
(** [with_async_none f] is a shorthand for:

    {[
      Lwt.with_value async_method_key (Some Async_none) f
    ]}

    @deprecated Will have no effect in Lwt 5.0.0. *)

val with_async_detach : (unit -> 'a) -> 'a
  [@@ocaml.deprecated
" Will have no effect in Lwt >= 5.0.0. See
   https://github.com/ocsigen/lwt/issues/572"]
(** [with_async_detach f] is a shorthand for:

    {[
      Lwt.with_value async_method_key (Some Async_detach) f
    ]}

    @deprecated Will have no effect in Lwt 5.0.0. *)

val with_async_switch : (unit -> 'a) -> 'a
  [@@ocaml.deprecated
" Will have no effect in Lwt >= 5.0.0. See
   https://github.com/ocsigen/lwt/issues/572"]
(** [with_async_switch f] is a shorthand for:

    {[
      Lwt.with_value async_method_key (Some Async_switch) f
    ]}

    @deprecated Will have no effect in Lwt 5.0.0. *)



(** {2 Low-level interaction} *)

exception Retry
  (** If an action raises {!Retry}, it will be requeued until the {b
      file descriptor} becomes readable/writable again. *)

exception Retry_read
  (** If an action raises {!Retry_read}, it will be requeued until the
      {b file descriptor} becomes readable. *)

exception Retry_write
  (** If an action raises {!Retry_read}, it will be requeued until the
      {b file descriptor} becomes writables. *)

type io_event = Read | Write

val wrap_syscall : io_event -> file_descr -> (unit -> 'a) -> 'a Lwt.t
  (** [wrap_syscall set fd action] wrap an action on a {b file
      descriptor}. It tries to execute action, and if it can not be
      performed immediately without blocking, it is registered for
      later.

      In the latter case, if the thread is canceled, [action] is
      removed from [set]. *)

val check_descriptor : file_descr -> unit
  (** [check_descriptor fd] raise an exception if [fd] is not in the
      state [Open]. *)

val register_action : io_event -> file_descr -> (unit -> 'a) -> 'a Lwt.t
  (** [register_action set fd action] registers [action] on [fd]. When
      [fd] becomes [readable]/[writable] [action] is called.

      Note:

      - you must call [check_descriptor fd] before calling
      [register_action]

      - you should prefer using {!wrap_syscall}
  *)

type 'a job
  (** Type of job descriptions. A job description describe how to call
      a C function and how to get its result. The C function may be
      executed in another system thread. *)

val run_job : ?async_method : async_method -> 'a job -> 'a Lwt.t
  (** [run_job ?async_method job] starts [job] and wait for its
      termination.

      The [~async_method] argument will be ignored in Lwt 5.0.0, and this
      function will always act as if [~async_method:Async_detach] is passed.

      The async method is chosen follow:
      - if the optional parameter [async_method] is specified, it is
        used,
      - otherwise if the local key {!async_method_key} is set in the
        current thread, it is used,
      - otherwise the default method (returned by
        {!default_async_method}) is used.

      If the method is [Async_none] then the job is run synchronously
      and may block the current system thread, thus blocking all Lwt
      threads.

      If the method is [Async_detach] then the job is run in another
      system thread, unless the the maximum number of worker threads
      has been reached (as given by {!pool_size}).

      If the method is [Async_switch] then the job is run
      synchronously and if it blocks, execution will continue in
      another system thread (unless the limit is reached).
  *)

val abort_jobs : exn -> unit
  (** [abort_jobs exn] make all pending jobs to fail with exn. Note
      that this does not abort the real job (i.e. the C function
      executing it), just the lwt thread for it. *)

val cancel_jobs : unit -> unit
  (** [cancel_jobs ()] is the same as [abort_jobs Lwt.Canceled]. *)

val wait_for_jobs : unit -> unit Lwt.t
  (** Wait for all pending jobs to terminate. *)

val execute_job :
  ?async_method : async_method ->
  job : 'a job ->
  result : ('a job -> 'b) ->
  free : ('a job -> unit) -> 'b Lwt.t
  [@@ocaml.deprecated " Use Lwt_unix.run_job."]
  (** @deprecated Use [run_job]. *)

(** {2 Notifications} *)

(** Lwt internally use a pipe to send notification to the main
    thread. The following functions allow to use this pipe. *)

val make_notification : ?once : bool -> (unit -> unit) -> int
  (** [new_notifier ?once f] registers a new notifier. It returns the
      id of the notifier. Each time a notification with this id is
      received, [f] is called.

      if [once] is specified, then the notification is stopped after
      the first time it is received. It defaults to [false]. *)

val send_notification : int -> unit
  (** [send_notification id] sends a notification.

      This function is thread-safe. *)

val stop_notification : int -> unit
  (** Stop the given notification. Note that you should not reuse the
      id after the notification has been stopped, the result is
      unspecified if you do so. *)

val call_notification : int -> unit
  (** Call the handler associated to the given notification. Note that
      if the notification was defined with [once = true] it is removed. *)

val set_notification : int -> (unit -> unit) -> unit
  (** [set_notification id f] replace the function associated to the
      notification by [f]. It raises [Not_found] if the given
      notification is not found. *)

(** {2 System threads pool} *)

(** If the program is using the async method [Async_detach] or
    [Async_switch], Lwt will launch system threads to execute
    blocking system calls asynchronously. *)

val pool_size : unit -> int
  (** Maximum number of system threads that can be started. If this
      limit is reached, jobs will be executed synchronously. *)

val set_pool_size : int -> unit
  (** Change the size of the pool. *)

val thread_count : unit -> int
  (** The number of system threads running (excluding this one). *)

val thread_waiting_count : unit -> int
  (** The number threads waiting for a job. *)

(** {2 CPUs} *)

val get_cpu : unit -> int
  (** [get_cpu ()] returns the number of the CPU the current thread is
      running on. *)

val get_affinity : ?pid : int -> unit -> int list
  (** [get_affinity ?pid ()] returns the list of CPUs the process with
      pid [pid] is allowed to run on. If [pid] is not specified then
      the affinity of the current process is returned. *)

val set_affinity : ?pid : int -> int list -> unit
  (** [set_affinity ?pid cpus] sets the list of CPUs the given process
      is allowed to run on. *)

(** {2 Versioned interfaces} *)

(** Versioned variants of APIs undergoing breaking changes. *)
module Versioned :
sig
  val bind_1 : file_descr -> sockaddr -> unit
    [@@ocaml.deprecated
" Deprecated in favor of Lwt_unix.bind. See
   https://github.com/ocsigen/lwt/issues/230"]
  (** Old version of {!Lwt_unix.bind}. The current {!Lwt_unix.bind} evaluates to
      a promise, because the internal [bind(2)] system call can block if the
      given socket is a Unix domain socket.

      @deprecated Use {!Lwt_unix.bind}.
      @since 2.7.0 *)

  val bind_2 : file_descr -> sockaddr -> unit Lwt.t
    [@@ocaml.deprecated
" In Lwt >= 3.0.0, this is an alias for Lwt_unix.bind."]
  (** Since Lwt 3.0.0, this is just an alias for {!Lwt_unix.bind}.

      @deprecated Use {!Lwt_unix.bind}.
      @since 2.7.0 *)

  val recv_msg_2 :
    socket:file_descr -> io_vectors:IO_vectors.t ->
      (int * Unix.file_descr list) Lwt.t
    [@@ocaml.deprecated
" In Lwt >= 5.0.0, this is an alias for Lwt_unix.recv_msg."]
  (** Since Lwt 5.0.0, this is an alias for {!Lwt_unix.recv_msg}.

      @deprecated Use {!Lwt_unix.recv_msg}.
      @since 4.3.0 *)

  val send_msg_2 :
    socket:file_descr -> io_vectors:IO_vectors.t -> fds:Unix.file_descr list ->
      int Lwt.t
    [@@ocaml.deprecated
" In Lwt >= 5.0.0, this is an alias for Lwt_unix.send_msg."]
  (** Since Lwt 5.0.0, this is an alias for {!Lwt_unix.send_msg}.

      @deprecated Use {!Lwt_unix.send_msg}.
      @since 4.3.0 *)
end

(**/**)

val run : 'a Lwt.t -> 'a
  [@@ocaml.deprecated " Use Lwt_main.run."]
  (** @deprecated Use [Lwt_main.run]. *)

val has_wait4 : bool
  [@@ocaml.deprecated " Use Lwt_sys.have `wait4."]
  (** @deprecated Use [Lwt_sys.have `wait4]. *)

val somaxconn : unit -> int
  [@@ocaml.deprecated " This is an internal function."]

val retained : 'a -> bool ref
  (** @deprecated Used for testing. *)

val read_bigarray :
  string -> file_descr -> IO_vectors._bigarray -> int -> int -> int Lwt.t
  [@@ocaml.deprecated " This is an internal function."]

val write_bigarray :
  string -> file_descr -> IO_vectors._bigarray -> int -> int -> int Lwt.t
  [@@ocaml.deprecated " This is an internal function."]