- since 4.14.0
type t = out_channel
The type of output channel.
type open_flag = open_flag =
open for reading.*)
open for writing.*)
open for appending: always write at end of file.*)
create the file if it does not exist.*)
empty the file if it already exists.*)
fail if Open_creat and the file already exists.*)
open in binary mode (no conversion).*)
open in text mode (may perform conversions).*)
open in non-blocking mode.*)
Opening modes for
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
val with_open_bin : string -> (t -> 'a) -> 'a
with_open_bin fn f opens a channel
oc on file
fn and returns
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
with_open_bin, but the channel is opened in text mode (see
with_open_bin, but can specify the opening mode and file permission, in case the file must be created (see
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
pos, then going back to this position using
seek will not work. For this programming idiom to work reliably and portably, the file must be opened in binary mode.
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 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
flush, which do nothing when applied to an already closed channel. Note that
close may raise
Sys_error if the operating system signals an error when flushing or closing.
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 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.
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
- raises Invalid_argument
lendo not designate a valid range of
val output_substring : t -> string -> int -> int -> unit
output but take a string as argument instead of a byte sequence.
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
This function has no effect under operating systems that do not distinguish between text mode and binary mode.
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
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