1Out_channel(3)                   OCaml library                  Out_channel(3)
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NAME

6       Out_channel - Output channels.
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Module

9       Module   Out_channel
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Documentation

12       Module Out_channel
13        : sig end
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16       Output channels.
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18
19       Since 4.14.0
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25       type t = out_channel
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27
28       The type of output channel.
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30
31       type open_flag = open_flag =
32        | Open_rdonly  (* open for reading.
33        *)
34        | Open_wronly  (* open for writing.
35        *)
36        | Open_append  (* open for appending: always write at end of file.
37        *)
38        | Open_creat  (* create the file if it does not exist.
39        *)
40        | Open_trunc  (* empty the file if it already exists.
41        *)
42        | Open_excl  (* fail if Open_creat and the file already exists.
43        *)
44        | Open_binary  (* open in binary mode (no conversion).
45        *)
46        | Open_text  (* open in text mode (may perform conversions).
47        *)
48        | Open_nonblock  (* open in non-blocking mode.
49        *)
50
51
52       Opening modes for Out_channel.open_gen .
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56       val stdout : t
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58       The standard output for the process.
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62       val stderr : t
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64       The standard error output for the process.
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68       val open_bin : string -> t
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70       Open  the  named  file  for writing, and return a new output channel on
71       that file, positioned at the beginning of the file. The file  is  trun‐
72       cated to zero length if it already exists. It is created if it does not
73       already exists.
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77       val open_text : string -> t
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79       Same as Out_channel.open_bin , but the file is opened in text mode,  so
80       that  newline  translation takes place during writes. On operating sys‐
81       tems that do not distinguish between text mode and  binary  mode,  this
82       function behaves like Out_channel.open_bin .
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86       val open_gen : open_flag list -> int -> string -> t
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89       open_gen  mode  perm  filename opens the named file for writing, as de‐
90       scribed above. The extra argument mode specifies the opening mode.  The
91       extra  argument  perm  specifies the file permissions, in case the file
92       must be created.  Out_channel.open_text  and  Out_channel.open_bin  are
93       special cases of this function.
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97       val with_open_bin : string -> (t -> 'a) -> 'a
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100       with_open_bin fn f opens a channel oc on file fn and returns f
101            oc  . After f returns, either with a value or by raising an excep‐
102       tion, oc is guaranteed to be closed.
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106       val with_open_text : string -> (t -> 'a) -> 'a
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108       Like Out_channel.with_open_bin , but the channel is opened in text mode
109       (see Out_channel.open_text ).
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113       val with_open_gen : open_flag list -> int -> string -> (t -> 'a) -> 'a
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115       Like  Out_channel.with_open_bin  , but can specify the opening mode and
116       file permission, in case  the  file  must  be  created  (see  Out_chan‐
117       nel.open_gen ).
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121       val seek : t -> int64 -> unit
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124       seek chan pos sets the current writing position to pos for channel chan
125       . This works only for regular files. On files of other kinds  (such  as
126       terminals, pipes and sockets), the behavior is unspecified.
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130       val pos : t -> int64
131
132       Return  the  current  writing position for the given channel.  Does not
133       work on channels opened with the Open_append flag (returns  unspecified
134       results).
135
136       For  files  opened in text mode under Windows, the returned position is
137       approximate (owing to end-of-line conversion);  in  particular,  saving
138       the current position with Out_channel.pos , then going back to this po‐
139       sition using Out_channel.seek will not work.  For this programming  id‐
140       iom  to  work  reliably and portably, the file must be opened in binary
141       mode.
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145       val length : t -> int64
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147       Return the size (number of characters) of the regular file on which the
148       given  channel  is  opened.  If the channel is opened on a file that is
149       not a regular file, the result is meaningless.
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153       val close : t -> unit
154
155       Close the given channel, flushing all buffered write operations.   Out‐
156       put  functions  raise  a Sys_error exception when they are applied to a
157       closed output channel, except Out_channel.close and Out_channel.flush ,
158       which  do nothing when applied to an already closed channel.  Note that
159       Out_channel.close may raise Sys_error if the operating  system  signals
160       an error when flushing or closing.
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164       val close_noerr : t -> unit
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166       Same as Out_channel.close , but ignore all errors.
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170       val flush : t -> unit
171
172       Flush  the  buffer associated with the given output channel, performing
173       all pending writes on that channel.  Interactive programs must be care‐
174       ful  about  flushing  standard  output  and standard error at the right
175       time.
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179       val flush_all : unit -> unit
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181       Flush all open output channels; ignore errors.
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185       val output_char : t -> char -> unit
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187       Write the character on the given output channel.
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191       val output_byte : t -> int -> unit
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193       Write one 8-bit integer (as the single character with that code) on the
194       given output channel. The given integer is taken modulo 256.
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198       val output_string : t -> string -> unit
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200       Write the string on the given output channel.
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204       val output_bytes : t -> bytes -> unit
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206       Write the byte sequence on the given output channel.
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210       val output : t -> bytes -> int -> int -> unit
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213       output  oc  buf  pos len writes len characters from byte sequence buf ,
214       starting at offset pos , to the given output channel oc .
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217       Raises Invalid_argument if pos and len do not designate a  valid  range
218       of buf .
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222       val output_substring : t -> string -> int -> int -> unit
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224       Same  as  Out_channel.output but take a string as argument instead of a
225       byte sequence.
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229       val set_binary_mode : t -> bool -> unit
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232       set_binary_mode oc true sets the channel oc to binary mode: no transla‐
233       tions take place during output.
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236       set_binary_mode oc false sets the channel oc to text mode: depending on
237       the operating system, some translations may take place  during  output.
238       For instance, under Windows, end-of-lines will be translated from \n to
239       \r\n .
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241       This function has no effect under operating systems that do not distin‐
242       guish between text mode and binary mode.
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246       val set_buffered : t -> bool -> unit
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249       set_buffered  oc  true  sets  the  channel oc to buffered mode. In this
250       mode, data output on oc will be buffered until either the internal buf‐
251       fer  is full or the function Out_channel.flush or Out_channel.flush_all
252       is called, at which point it will be sent to the output device.
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255       set_buffered oc false sets the channel oc to unbuffered mode.  In  this
256       mode, data output on oc will be sent to the output device immediately.
257
258       All channels are open in buffered mode by default.
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262       val is_buffered : t -> bool
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265       is_buffered  oc  returns  whether  the  channel  oc  is  buffered  (see
266       Out_channel.set_buffered ).
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272OCamldoc                          2022-07-22                    Out_channel(3)