(**************************************************************************)
(*                                                                        *)
(*                                 OCaml                                  *)
(*                                                                        *)
(*             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 Lesser General Public License version 2.1, with the          *)
(*   special exception on linking described in the file LICENSE.          *)
(*                                                                        *)
(**************************************************************************)

(** System interface.

  Every function in this module raises [Sys_error] with an
  informative message when the underlying system call signal
  an error.
*)

external argv : string array = "%sys_argv"
(** The command line arguments given to the process.
   The first element is the command name used to invoke the program.
   The following elements are the command-line arguments
   given to the program. *)

val executable_name : string
(** The name of the file containing the executable currently running.
    This name may be absolute or relative to the current directory, depending
    on the platform and whether the program was compiled to bytecode or a native
    executable. *)

external file_exists : string -> bool = "caml_sys_file_exists"
(** Test if a file with the given name exists. *)

external is_directory : string -> bool = "caml_sys_is_directory"
(** Returns [true] if the given name refers to a directory,
    [false] if it refers to another kind of file.
    Raise [Sys_error] if no file exists with the given name.
    @since 3.10.0
*)

external remove : string -> unit = "caml_sys_remove"
(** Remove the given file name from the file system. *)

external rename : string -> string -> unit = "caml_sys_rename"
(** Rename a file.  [rename oldpath newpath] renames the file
    called [oldpath], giving it [newpath] as its new name,
    moving it between directories if needed.  If [newpath] already
    exists, its contents will be replaced with those of [oldpath].
    Depending on the operating system, the metadata (permissions,
    owner, etc) of [newpath] can either be preserved or be replaced by
    those of [oldpath].
   @since 4.06 concerning the "replace existing file" behavior *)

external getenv : string -> string = "caml_sys_getenv"
(** Return the value associated to a variable in the process
   environment. Raise [Not_found] if the variable is unbound. *)

val getenv_opt: string -> string option
(** Return the value associated to a variable in the process
    environment or [None] if the variable is unbound.
    @since 4.05
*)

external command : string -> int = "caml_sys_system_command"
(** Execute the given shell command and return its exit code. *)

external time : unit -> (float [@unboxed]) =
  "caml_sys_time" "caml_sys_time_unboxed" [@@noalloc]
(** Return the processor time, in seconds, used by the program
   since the beginning of execution. *)

external chdir : string -> unit = "caml_sys_chdir"
(** Change the current working directory of the process. *)

external getcwd : unit -> string = "caml_sys_getcwd"
(** Return the current working directory of the process. *)

external readdir : string -> string array = "caml_sys_read_directory"
(** Return the names of all files present in the given directory.
   Names denoting the current directory and the parent directory
   (["."] and [".."] in Unix) are not returned.  Each string in the
   result is a file name rather than a complete path.  There is no
   guarantee that the name strings in the resulting array will appear
   in any specific order; they are not, in particular, guaranteed to
   appear in alphabetical order. *)

val interactive : bool ref
(** This reference is initially set to [false] in standalone
   programs and to [true] if the code is being executed under
   the interactive toplevel system [ocaml]. *)

val os_type : string
(** Operating system currently executing the OCaml program. One of
-  ["Unix"] (for all Unix versions, including Linux and Mac OS X),
-  ["Win32"] (for MS-Windows, OCaml compiled with MSVC++ or Mingw),
-  ["Cygwin"] (for MS-Windows, OCaml compiled with Cygwin). *)

type backend_type =
  | Native
  | Bytecode
  | Other of string (**)
(** Currently, the official distribution only supports [Native] and
    [Bytecode], but it can be other backends with alternative
    compilers, for example, javascript.

    @since 4.04.0
*)

val backend_type : backend_type
(** Backend type  currently executing the OCaml program.
    @since 4.04.0
 *)

val unix : bool
(** True if [Sys.os_type = "Unix"].
    @since 4.01.0 *)

val win32 : bool
(** True if [Sys.os_type = "Win32"].
    @since 4.01.0 *)

val cygwin : bool
(** True if [Sys.os_type = "Cygwin"].
    @since 4.01.0 *)

val word_size : int
(** Size of one word on the machine currently executing the OCaml
    program, in bits: 32 or 64. *)

val int_size : int
(** Size of [int], in bits. It is 31 (resp. 63) when using OCaml on a
    32-bit (resp. 64-bit) platform. It may differ for other implementations,
    e.g. it can be 32 bits when compiling to JavaScript.
    @since 4.03.0 *)

val big_endian : bool
(** Whether the machine currently executing the Caml program is big-endian.
    @since 4.00.0 *)

val max_string_length : int
(** Maximum length of strings and byte sequences. *)

val max_array_length : int
(** Maximum length of a normal array (i.e. any array whose elements are
    not of type [float]). The maximum length of a [float array]
    is [max_floatarray_length] if OCaml was configured with
    [--enable-flat-float-array] and [max_array_length] if configured
    with [--disable-flat-float-array]. *)

val max_floatarray_length : int
(** Maximum length of a floatarray. This is also the maximum length of
    a [float array] when OCaml is configured with
    [--enable-flat-float-array]. *)

external runtime_variant : unit -> string = "caml_runtime_variant"
(** Return the name of the runtime variant the program is running on.
    This is normally the argument given to [-runtime-variant] at compile
    time, but for byte-code it can be changed after compilation.
    @since 4.03.0 *)

external runtime_parameters : unit -> string = "caml_runtime_parameters"
(** Return the value of the runtime parameters, in the same format
    as the contents of the [OCAMLRUNPARAM] environment variable.
    @since 4.03.0 *)


(** {1 Signal handling} *)


type signal_behavior =
    Signal_default
  | Signal_ignore
  | Signal_handle of (int -> unit)   (** *)
(** What to do when receiving a signal:
   - [Signal_default]: take the default behavior
     (usually: abort the program)
   - [Signal_ignore]: ignore the signal
   - [Signal_handle f]: call function [f], giving it the signal
   number as argument. *)

external signal :
  int -> signal_behavior -> signal_behavior = "caml_install_signal_handler"
(** Set the behavior of the system on receipt of a given signal.  The
   first argument is the signal number.  Return the behavior
   previously associated with the signal. If the signal number is
   invalid (or not available on your system), an [Invalid_argument]
   exception is raised. *)

val set_signal : int -> signal_behavior -> unit
(** Same as {!Sys.signal} but return value is ignored. *)


(** {2 Signal numbers for the standard POSIX signals.} *)

val sigabrt : int
(** Abnormal termination *)

val sigalrm : int
(** Timeout *)

val sigfpe : int
(** Arithmetic exception *)

val sighup : int
(** Hangup on controlling terminal *)

val sigill : int
(** Invalid hardware instruction *)

val sigint : int
(** Interactive interrupt (ctrl-C) *)

val sigkill : int
(** Termination (cannot be ignored) *)

val sigpipe : int
(** Broken pipe *)

val sigquit : int
(** Interactive termination *)

val sigsegv : int
(** Invalid memory reference *)

val sigterm : int
(** Termination *)

val sigusr1 : int
(** Application-defined signal 1 *)

val sigusr2 : int
(** Application-defined signal 2 *)

val sigchld : int
(** Child process terminated *)

val sigcont : int
(** Continue *)

val sigstop : int
(** Stop *)

val sigtstp : int
(** Interactive stop *)

val sigttin : int
(** Terminal read from background process *)

val sigttou : int
(** Terminal write from background process *)

val sigvtalrm : int
(** Timeout in virtual time *)

val sigprof : int
(** Profiling interrupt *)

val sigbus : int
(** Bus error
    @since 4.03 *)

val sigpoll : int
(** Pollable event
    @since 4.03 *)

val sigsys : int
(** Bad argument to routine
    @since 4.03 *)

val sigtrap : int
(** Trace/breakpoint trap
    @since 4.03 *)

val sigurg : int
(** Urgent condition on socket
    @since 4.03 *)

val sigxcpu : int
(** Timeout in cpu time
    @since 4.03 *)

val sigxfsz : int
(** File size limit exceeded
    @since 4.03 *)


exception Break
(** Exception raised on interactive interrupt if {!Sys.catch_break}
   is on. *)


val catch_break : bool -> unit
(** [catch_break] governs whether interactive interrupt (ctrl-C)
   terminates the program or raises the [Break] exception.
   Call [catch_break true] to enable raising [Break],
   and [catch_break false] to let the system
   terminate the program on user interrupt. *)


val ocaml_version : string
(** [ocaml_version] is the version of OCaml.
    It is a string of the form ["major.minor[.patchlevel][+additional-info]"],
    where [major], [minor], and [patchlevel] are integers, and
    [additional-info] is an arbitrary string. The [[.patchlevel]] and
    [[+additional-info]] parts may be absent. *)


val enable_runtime_warnings: bool -> unit
(** Control whether the OCaml runtime system can emit warnings
    on stderr.  Currently, the only supported warning is triggered
    when a channel created by [open_*] functions is finalized without
    being closed.  Runtime warnings are enabled by default.

    @since 4.03.0 *)

val runtime_warnings_enabled: unit -> bool
(** Return whether runtime warnings are currently enabled.

    @since 4.03.0 *)

(** {1 Optimization} *)

external opaque_identity : 'a -> 'a = "%opaque"
(** For the purposes of optimization, [opaque_identity] behaves like an
    unknown (and thus possibly side-effecting) function.

    At runtime, [opaque_identity] disappears altogether.

    A typical use of this function is to prevent pure computations from being
    optimized away in benchmarking loops.  For example:
    {[
      for _round = 1 to 100_000 do
        ignore (Sys.opaque_identity (my_pure_computation ()))
      done
    ]}

    @since 4.03.0
*)
