<tt>io</tt>: buffered input and output

`io`: buffered input and output

type in_channel
type out_channel

The abstract types of input channels and output channels.

exception End_of_file

Raised when an operation cannot complete, because the end of the file has been reached.

value stdin : in_channel
value std_in : in_channel
value stdout : out_channel
value std_out : out_channel
value stderr : out_channel
value std_err : out_channel

The standard input, standard output, and standard error output for the process. std_in, std_out and std_err are respectively synonymous with stdin, stdout and stderr.

value exit : int -> 'a

Flush all pending writes on std_out and std_err, and terminate the process, returning the given status code to the operating system (usually 0 to indicate no errors, and a small positive integer to indicate failure.) This function should be called at the end of all standalone programs that output results on std_out or std_err; otherwise, the program may appear to produce no output, or its output may be truncated.

Output functions on standard output

value print_char : char -> unit

Print the character on standard output.

value print_string : string -> unit

Print the string on standard output.

value print_int : int -> unit

Print the integer, in decimal, on standard output.

value print_float : float -> unit

Print the floating-point number, in decimal, on standard output.

value print_endline : string -> unit

Print the string, followed by a newline character, on standard output.

value print_newline : unit -> unit

Print a newline character on standard output, and flush standard output. This can be used to simulate line buffering of standard output.

Output functions on standard error

value prerr_char : char -> unit

Print the character on standard error.

value prerr_string : string -> unit

Print the string on standard error.

value prerr_int : int -> unit

Print the integer, in decimal, on standard error.

value prerr_float : float -> unit

Print the floating-point number, in decimal, on standard error.

value prerr_endline : string -> unit

Print the string, followed by a newline character on standard error and flush standard error.

Input functions on standard input

value read_line : unit -> string

Flush standard output, then read characters from standard input until a newline character is encountered. Return the string of all characters read, without the newline character at the end.

value read_int : unit -> int

Flush standard output, then read one line from standard input and convert it to an integer. Raise Failure "int_of_string" if the line read is not a valid representation of an integer.

value read_float : unit -> float

Flush standard output, then read one line from standard input and convert it to a floating-point number. The result is unspecified if the line read is not a valid representation of a floating-point number.

General output functions

value open_out : string -> out_channel

Open the named file for writing, and return a new output channel on that file, positionned 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. Raise sys__Sys_error if the file could not be opened.

value open_out_bin : string -> out_channel

Same as open_out, but the file is opened in binary mode, so that no translation takes place during writes. On operating systems that do not distinguish between text mode and binary mode, this function behaves like open_out.

value open_out_gen : sys__open_flag list -> int -> string -> out_channel

open_out_gen mode rights filename opens the file named filename for writing, as above. The extra argument mode specify the opening mode (see sys__open). The extra argument rights specifies the file permissions, in case the file must be created (see sys__open). open_out and open_out_bin are special cases of this function.

value open_descriptor_out : int -> out_channel

open_descriptor_out fd returns a buffered output channel writing to the file descriptor fd. The file descriptor fd must have been previously opened for writing, else the behavior is undefined.

value flush : out_channel -> unit

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

value output_char : out_channel -> char -> unit

Write the character on the given output channel.

value output_string : out_channel -> string -> unit

Write the string on the given output channel.

value output : out_channel -> string -> int -> int -> unit

output chan buff ofs len writes len characters from string buff, starting at offset ofs, to the output channel chan. Raise Invalid_argument "output" if ofs and len do not designate a valid substring of buff.

value output_byte : out_channel -> 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.

value output_binary_int : out_channel -> int -> unit

Write one integer in binary format on the given output channel. The only reliable way to read it back is through the input_binary_int function. The format is compatible across all machines for a given version of Caml Light.

value output_value : out_channel -> 'a -> unit

Write the representation of a structured value of any type to a channel. Circularities and sharing inside the value are detected and preserved. The object can be read back, by the function input_value. The format is compatible across all machines for a given version of Caml Light.

value output_compact_value : out_channel -> 'a -> unit

Same as output_value, but uses a different format, which occupies less space on the file, but takes more time to generate and read back.

value seek_out : out_channel -> int -> unit

seek_out 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.

value pos_out : out_channel -> int

Return the current writing position for the given channel.

value out_channel_length : out_channel -> int

Return the total length (number of characters) of the given channel. This works only for regular files. On files of other kinds, the result is meaningless.

value close_out : out_channel -> unit

Close the given channel, flushing all buffered write operations. The behavior is unspecified if any of the functions above is called on a closed channel.

General input functions

value open_in : string -> in_channel

Open the named file for reading, and return a new input channel on that file, positionned at the beginning of the file. Raise sys__Sys_error if the file could not be opened.

value open_in_bin : string -> in_channel

Same as open_in, but the file is opened in binary mode, so that no translation takes place during reads. On operating systems that do not distinguish between text mode and binary mode, this function behaves like open_in.

value open_in_gen : sys__open_flag list -> int -> string -> in_channel

open_in_gen mode rights filename opens the file named filename for reading, as above. The extra arguments mode and rights specify the opening mode and file permissions (see sys__open). open_in and open_in_bin are special cases of this function.

value open_descriptor_in : int -> in_channel

open_descriptor_in fd returns a buffered input channel reading from the file descriptor fd. The file descriptor fd must have been previously opened for reading, else the behavior is undefined.

value input_char : in_channel -> char

Read one character from the given input channel. Raise End_of_file if there are no more characters to read.

value input_line : in_channel -> string

Read characters from the given input channel, until a newline character is encountered. Return the string of all characters read, without the newline character at the end. Raise End_of_file if the end of the file is reached at the beginning of line.

value input : in_channel -> string -> int -> int -> int

input chan buff ofs len attempts to read len characters from channel chan, storing them in string buff, starting at character number ofs. It returns the actual number of characters read, between 0 and len (inclusive). A return value of 0 means that the end of file was reached. A return value between 0 and len exclusive means that no more characters were available at that time; input must be called again to read the remaining characters, if desired. Exception Invalid_argument "input" is raised if ofs and len do not designate a valid substring of buff.

value really_input : in_channel -> string -> int -> int -> unit

really_input chan buff ofs len reads len characters from channel chan, storing them in string buff, starting at character number ofs. Raise End_of_file if the end of file is reached before len characters have been read. Raise Invalid_argument "really_input" if ofs and len do not designate a valid substring of buff.

value input_byte : in_channel -> int

Same as input_char, but return the 8-bit integer representing the character. Raise End_of_file if an end of file was reached.

value input_binary_int : in_channel -> int

Read an integer encoded in binary format from the given input channel. See output_binary_int. Raise End_of_file if an end of file was reached while reading the integer.

value input_value : in_channel -> 'a

Read the representation of a structured value, as produced by output_value or output_compact_value, and return the corresponding value. This is not type-safe. The type of the returned object is not 'a properly speaking: the returned object has one unique type, which cannot be determined at compile-time. The programmer should explicitly give the expected type of the returned value, using the following syntax: (input_value chan : type). The behavior is unspecified if the object in the file does not belong to the given type.

value seek_in : in_channel -> int -> unit

seek_in chan pos sets the current reading position to pos for channel chan. This works only for regular files. On files of other kinds, the behavior is unspecified.

value pos_in : in_channel -> int

Return the current reading position for the given channel.

value in_channel_length : in_channel -> int