NAME

       Out_channel - Output channels.

Module

       Module   Out_channel

Documentation

       Module Out_channel
        : sig end

       Output channels.

       This module provides functions for working with output channels.

       See Out_channel.examples below.

       Since 4.14

   Channels
       type t = out_channel

       The type of output channel.

       type open_flag = open_flag =
        | Open_rdonly  (* open for reading.
        *)
        | Open_wronly  (* open for writing.
        *)
        | Open_append  (* open for appending: always write at end of file.
        *)
        | Open_creat  (* create the file if it does not exist.
        *)
        | Open_trunc  (* empty the file if it already exists.
        *)
        | Open_excl  (* fail if Open_creat and the file already exists.
        *)
        | Open_binary  (* open in binary mode (no conversion).
        *)
        | Open_text  (* open in text mode (may perform conversions).
        *)
        | Open_nonblock  (* open in non-blocking mode.
        *)

       Opening modes for Out_channel.open_gen .

       val stdout : t

       The standard output for the process.

       val stderr : t

       The standard error output for the process.

       val open_bin : string -> t

       Open  the  named  file  for  writing,  and  return  a  new output channel on that file, positioned at the
       beginning of the file. The file is truncated to zero length if it already exists. It  is  created  if  it
       does not already exists.

       val open_text : string -> t

       Same  as  Out_channel.open_bin  ,  but the file is opened in text mode, so that newline translation takes
       place during writes. On operating systems that do not distinguish between text mode and binary mode, this
       function behaves like Out_channel.open_bin .

       val open_gen : open_flag list -> int -> string -> t

       open_gen mode perm filename opens the named file for writing, as described above. The extra argument mode
       specifies the opening mode. The extra argument perm specifies the file permissions, in case the file must
       be created.  Out_channel.open_text and Out_channel.open_bin are special cases of this function.

       val with_open_bin : string -> (t -> 'a) -> 'a

       with_open_bin fn f opens a channel oc on file fn and returns f
           oc . After f returns, either with a value or by raising an exception, oc is guaranteed to be closed.

       val with_open_text : string -> (t -> 'a) -> 'a

       Like Out_channel.with_open_bin , but the channel is opened in text mode (see Out_channel.open_text ).

       val with_open_gen : open_flag list -> int -> string -> (t -> 'a) -> 'a

       Like Out_channel.with_open_bin , but can specify the opening mode and file permission, in case  the  file
       must be created (see Out_channel.open_gen ).

       val close : t -> unit

       Close  the  given  channel,  flushing  all buffered write operations.  Output functions raise a Sys_error
       exception  when  they  are  applied  to  a  closed   output   channel,   except   Out_channel.close   and
       Out_channel.flush   ,   which  do  nothing  when  applied  to  an  already  closed  channel.   Note  that
       Out_channel.close may raise Sys_error if the operating system signals an error when flushing or closing.

       val close_noerr : t -> unit

       Same as Out_channel.close , but ignore all errors.

   Output
       val output_char : t -> char -> unit

       Write the character on the given output channel.

       val output_byte : t -> int -> unit

       Write one 8-bit integer (as the single character with that code) on the given output channel.  The  given
       integer is taken modulo 256.

       val output_string : t -> string -> unit

       Write the string on the given output channel.

       val output_bytes : t -> bytes -> unit

       Write the byte sequence on the given output channel.

   Advanced output
       val output : t -> bytes -> int -> int -> unit

       output  oc  buf  pos  len  writes len characters from byte sequence buf , starting at offset pos , to the
       given output channel oc .

       Raises Invalid_argument if pos and len do not designate a valid range of buf .

       val output_substring : t -> string -> int -> int -> unit

       Same as Out_channel.output but take a string as argument instead of a byte sequence.

       val output_bigarray : t -> ('a, Bigarray.int8_unsigned_elt, Bigarray.c_layout) Bigarray.Array1.t  ->  int
       -> int -> unit

       Same as Out_channel.output but take the data from a bigarray.

       Since 5.2

   Flushing
       val flush : t -> unit

       Flush the buffer associated with the given output channel, performing all pending writes on that channel.
       Interactive programs must be careful about flushing standard output and standard error at the right time.

       val flush_all : unit -> unit

       Flush all open output channels; ignore errors.

   Seeking
       val seek : t -> int64 -> unit

       seek  chan  pos  sets  the current writing position to pos for channel chan . This works only for regular
       files. On files of other kinds (such as terminals, pipes and sockets), the behavior is unspecified.

       val pos : t -> int64

       Return the current writing position for the given channel.  Does not work on  channels  opened  with  the
       Open_append flag (returns unspecified results).

       For  files  opened in text mode under Windows, the returned position is approximate (owing to end-of-line
       conversion); in particular, saving the current position with Out_channel.pos , then going  back  to  this
       position using Out_channel.seek will not work.  For this programming idiom to work reliably and portably,
       the file must be opened in binary mode.

   Attributes
       val length : t -> int64

       Return  the size (number of characters) of the regular file on which the given channel is opened.  If the
       channel is opened on a file that is not a regular file, the result is meaningless.

       val set_binary_mode : t -> bool -> unit

       set_binary_mode oc true sets the channel oc to binary mode: no translations take place during output.

       set_binary_mode oc false sets the channel oc to text  mode:  depending  on  the  operating  system,  some
       translations  may take place during output.  For instance, under Windows, end-of-lines will be translated
       from \n to \r\n .

       This function has no effect under operating systems that do not distinguish between text mode and  binary
       mode.

       val is_binary_mode : t -> bool

       is_binary_mode oc returns whether the channel oc is in binary mode (see Out_channel.set_binary_mode ).

       Since 5.2

       val set_buffered : t -> bool -> unit

       set_buffered  oc  true  sets  the  channel  oc  to buffered mode. In this mode, data output on oc will be
       buffered  until  either  the  internal  buffer   is   full   or   the   function   Out_channel.flush   or
       Out_channel.flush_all is called, at which point it will be sent to the output device.

       set_buffered  oc  false  sets  the channel oc to unbuffered mode. In this mode, data output on oc will be
       sent to the output device immediately.

       All channels are open in buffered mode by default.

       val is_buffered : t -> bool

       is_buffered oc returns whether the channel oc is buffered (see Out_channel.set_buffered ).

       val isatty : t -> bool

       isatty oc is true if oc refers to a terminal or console window, false otherwise.

       Since 5.1

   Examples
       Writing the contents of a file:
             let write_file file s =
               Out_channel.with_open_bin file
                 (fun oc -> Out_channel.output_string oc s))

OCamldoc                                           2025-01-27                                    Out_channel(3o)