(** An output channel for doing blocking writes to destinations like files and sockets.
Note that an [Out_channel.t] is a custom block with a finalizer, and so is allocated
directly to the major heap. Creating a lot of out_channels can result in many major
collections and poor performance.
Note that this is simply another interface on the [out_channel] type in the OCaml
standard library.
As for the output functions in the standard library, all the functions in this module,
unless otherwise specified, can raise [Sys_error] when the system calls they invoke
fail.
*)
open! Base
open! Import
type t = Caml.out_channel [@@deriving_inline sexp_of]
include
sig [@@@ocaml.warning "-32"] val sexp_of_t : t -> Ppx_sexp_conv_lib.Sexp.t
end[@@ocaml.doc "@inline"]
[@@@end]
include Equal.S with type t := t
val stdout : t
val stderr : t
type 'a with_create_args =
?binary:bool (** defaults to [true] *)
-> ?append:bool (** defaults to [false] *)
-> ?fail_if_exists:bool (** defaults to [false] *)
-> ?perm:int
-> 'a
val create : (string -> t) with_create_args
val with_file : (string -> f:(t -> 'a) -> 'a) with_create_args
(** [close t] flushes and closes [t], and may raise an exception. [close] returns () and
does not raise if [t] is already closed. [close] raises an exception if the close()
system call on the underlying file descriptor fails (i.e. returns -1), which would
happen in the following cases:
EBADF -- this would happen if someone else did close() system call on the underlying
fd, which I would think a rare event.
EINTR -- would happen if the system call was interrupted by a signal, which would be
rare. Also, I think we should probably just catch EINTR and re-attempt the close.
Unfortunately, we can't do that in OCaml because the OCaml library marks the
out_channel as closed even if the close syscall fails, so a subsequent call
[close_out_channel] will be a no-op. This should really be fixed in the OCaml library
C code, having it restart the close() syscall on EINTR. I put a couple CRs in
[fixed_close_channel], our rework of OCaml's [caml_ml_close_channel],
EIO -- I don't recall seeing this. I think it's rare.
See "man 2 close" for details.
*)
val close : t -> unit
(** [close_no_err] tries to flush and close [t]. It does not raise.*)
val close_no_err : t -> unit
val set_binary_mode : t -> bool -> unit
val flush : t -> unit
val output : t -> buf:bytes -> pos:int -> len:int -> unit
val output_string : t -> string -> unit
val output_substring : t -> buf:string -> pos:int -> len:int -> unit
val output_bytes : t -> Bytes.t -> unit
val output_char : t -> char -> unit
val output_byte : t -> int -> unit
val output_binary_int : t -> int -> unit
val output_buffer : t -> Buffer.t -> unit
val output_value : t -> _ -> unit (** OCaml's internal Marshal format *)
val newline : t -> unit
(** Outputs a list of lines, each terminated by a newline character *)
val output_lines : t -> string list -> unit
(** Formatted printing to an out channel. This is the same as [Printf.sprintf] except
that it outputs to [t] instead of returning a string. Similarly, the function
arguments corresponding to conversions specifications such as [%a] or [%t] takes [t]
as argument and must print to it instead of returning a string. *)
val fprintf : t -> ('a, t, unit) format -> 'a
(** [printf fmt] is the same as [fprintf stdout fmt] *)
val printf : ('a, t, unit) format -> 'a
(** [print_s sexp] outputs [sexp] on [stdout], by default using [Sexp.to_string_hum],
or, with [~mach:()], [Sexp.to_string_mach]. *)
val print_s : ?mach : unit -> Sexp.t -> unit
(** [eprint_s sexp] outputs [sexp] on [stderr], by default using [Sexp.to_string_hum],
or, with [~mach:()], [Sexp.to_string_mach]. *)
val eprint_s : ?mach : unit -> Sexp.t -> unit
(** [eprintf fmt] is the same as [fprintf stderr fmt] *)
val eprintf : ('a, t, unit) format -> 'a
(** [kfprintf k t fmt] is the same as [fprintf t fmt], but instead of returning
immediately, passes the out channel to [k] at the end of printing. *)
val kfprintf : (t -> 'a) -> t -> ('b, t, unit, 'a) format4 -> 'b
(** [print_string s] = [output_string stdout s] *)
val print_string : string -> unit
(** [print_endline str] outputs [str] to [stdout] followed by a newline then flushes
[stdout] *)
val print_endline : string -> unit
(** [prerr_endline str] outputs [str] to [stderr] followed by a newline then flushes
[stderr] *)
val prerr_endline : string -> unit
val seek : t -> int64 -> unit
val pos : t -> int64
val length : t -> int64
(** The first argument of these is the file name to write to. *)
val write_lines : string -> string list -> unit
val write_all : string -> data:string -> unit