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I/O library#

Importing#

|#| 'stdio.nest' = io

Functions#

@can_read#

Synopsis:

[file: IOFile] @can_read -> Bool

Returns:

true if file can be read and false otherwise.

@can_seek#

Synopsis:

[file: IOFile] @can_seek -> Bool

Returns:

true if file can be sought and false otherwise.

@can_write#

Synopsis:

[file: IOFile] @can_write -> Bool

Returns:

true if file can be written and false otherwise.

@close#

Synopsis:

[file: IOFile] @close -> null

Description:

Closes a file. After a file is closed, you will not be able to do any other operation with it. If the file was already closed an error is thrown. When the program ends any file that is still open gets closed.

Arguments:

  • file: the file to close

@descriptor#

Synopsis:

[file: IOFile] @descriptor -> Int

Returns:

The file descriptor of a given file. If the file is closed or does not have a descriptor -1 is returned and no error is thrown.

@encoding#

Synopsis:

[file: IOFile] @encoding -> Str

Returns:

The encoding of the file as a string. If the file is closed or in binary mode this function fails.

@file_size#

Synopsis:

[file: IOFile] @file_size -> Int

Returns:

The size of the file in bytes. Throws an error if the file cannot be sought or is closed.

@flush#

Synopsis:

[file: IOFile] @flush -> null

Description:

Flushes the output buffer of a file. An error is thrown if the file is closed or cannot be written.

@get_flags#

Synopsis:

[file: IOFile] @get_flags -> Str

Returns:

A 5-character string where each character represents a flag as follows:

  1. r if the file is readable
  2. w if the file is writable
  3. b if the file is binary
  4. s if the file can be sought
  5. t if the file is a TTY

If file does not have a flag, that character is replaced by a hyphen (-).

Example:

|#| 'stdio.nest' = io

'a.txt' 'w' @io.open = f1
>>> (f1 @io.get_flags '\n' ><) --> '-w-s-'
f1 @io.close

'a.txt' 'r+' @io.open = f2
>>> (f2 @io.get_flags '\n' ><) --> 'rw-s-'
f2 @io.close

'a.txt' 'rb' @io.open = f3
>>> (f3 @io.get_flags '\n' ><) --> 'r-bs-'
f3 @io.close

@is_a_tty#

Synopsis:

[file: IOFile] @is_a_tty -> Bool

Returns:

true if file is a TTY and false otherwise.

@is_bin#

Synopsis:

[file: IOFile] @is_bin -> Bool

Returns:

true if file was opened in binary mode and false otherwise.

@open#

Synopsis:

[path: Str, mode: Str?, encoding: Str?, buf_size: Int?] @open -> IOFile

Description:

Opens a file. If the mode is null it is set to r. If encoding is null it is set to utf8. If buf_size is null it is set to 512 bytes.

The file modes are:

Mode Description
w write, destroying the contents
wb write bytes, destroying the contents
r read
rb read bytes
a append
ab append bytes
r+ read and write, keeping the contents
rb+ or r+b read and write bytes, keeping the contents
w+ read and write, destroying the contents
wb+ or w+b read and write bytes, destroying the contents
a+ read and append, keeping the contents
ab+ or a+b read and append bytes, keeping the contents

To see all available encodings check this page.

Arguments:

  • path: the path of the file to open
  • mode: the mode in which it should be opened
  • encoding: the encoding used to open the file, if mode is binary this argument must be null
  • buf_size: the size of the buffer of the file

Returns:

An IOFile object or null if the file was not found.

@println#

Synopsis:

[object: Any, flush: Bool?, file: IOFile?] @println -> null

Description:

Will print object like >>> followed by a newline. flush, if null, defaults to false. file, if null, is stdout by default. If file is closed or cannot be written an error is thrown.

Arguments:

  • object: the object to be printed
  • flush: whether the file should be flushed
  • file: the file to write to

@read#

Synopsis:

[file: IOFile, size: Int?] @read -> Str

Description:

Reads a number of characters from a file opened in r, r+, w+ or a+ and returns a Str object. If size is negative or null the whole file is read.

Warning

The file cannot be read entirely if it cannot be sought. If you try to read a file that cannot be sought while omitting the size or giving it a negative value an error is thrown.

Arguments:

  • file: the file to be read
  • size: the number or characters to read

Returns:

The content that it read as a string.

@read_bytes#

Synopsis:

[file: IOFile, size: Int?] @read_bytes -> Array.Byte

Description:

Reads a number of bytes from a file opened in rb, rb+, wb+ or ab+ and returns an Array object. To convert the array to a string, use the decode function in stdsutil.nest. If size is negative or null the whole file is read.

Warning

The file cannot be read entirely if it cannot be sought. If you try to read a file that cannot be sought while omitting the size or giving it a negative value an error is thrown.

Arguments:

  • file: the file to be read
  • size: the number of bytes to read

Returns:

The content that it read as an array of Byte objects.

@seek#

Synopsis:

[file: IOFile, starting_position: Int?, offset: Int?] @seek -> Int

Description:

Moves the file position indicator from starting_position by offset bytes. An error is thrown if the file is closed, cannot be sought or if the file position indicator would go outside the file.

If starting_position is null, FROM_CUR will be used.

If offset is null, 0 will be used.

Arguments:

  • file: the file of which the file position indicator should be moved
  • starting_position: the position from which the offset is applied, this can be either FROM_START, FROM_CUR or FROM_END
  • offset: the offset in bytes from the starting position, it can be negative

Returns:

The end position of the indicator in bytes from the start of the file. Calling this function without starting_position and offset will simply return the current position (like ftell in C).

@virtual_file#

Synopsis:

[binary: Bool?, buffer_size: Int?] @virtual_file -> IOFile

Creates a virtual IOFile object that works like a normal file but is not an actual file.

Arguments:

  • binary: specifies if the file should use write and read or write_bytes and read_bytes. If set to null it is interpreted as false.
  • buffer_size specifies the initial size of the file in bytes

Returns:

The newly created file.

@write#

Synopsis:

[file: IOFile, content: Any] @write -> Int

Description:

Writes to a file opened in w, a, r+, w+ or a+. content is casted to a string before being written. If the file is closed an error is thrown.

Arguments:

  • file: the file to be written
  • content: the contents to be written

Returns:

The number of characters written.

Example:

|#| 'stdio.nest' = io

'example.txt' 'w' @io.open = f
f {1, 2, 3} @io.write
f @io.close
'example.txt' @io.open = f
f @io.read @io.println --> '{1, 2, 3}'
f @io.close

@write_bytes#

Synopsis:

[file: IOFile, content: Array|Vector.Byte] @write_bytes -> Int

Description:

Writes to a binary file opened in wb, ab, rb+, wb+ or ab+. The second argument is an array or vector containing only Byte objects. To create such vector from a string, use the encode function in stdsutil.nest.

Arguments:

  • file: the file to be written
  • content: the sequence of bytes to write

Returns:

The number of bytes written.

@_get_stdin#

Synopsis:

[] @_get_stdin -> IOFile

Returns:

The current input stream. If _set_stdin is never called this will return the same object that STDIN points to.

@_get_stderr#

Synopsis:

[] @_get_stdin -> IOFile

Returns:

The current error stream. If _set_stderr is never called this will return the same object that STDERR points to.

@_get_stdout#

Synopsis:

[] @_get_stdin -> IOFile

Returns:

The current output stream. If _set_stdout is never called this will return the same object that STDOUT points to.

@_set_stdin#

Synopsis:

[file: IOFile] @_set_stdin -> null

Description:

Changes the standard input stream to file. file must support reading and must not be already closed.

The STDIN constant will not reflect any changes and will always point to the original input stream unless changed manually.

@_set_stderr#

Synopsis:

[file: IOFile] @_set_stderr -> null

Description:

Changes the standard error stream to file. file must support writing and must not be already closed.

The STDERR constant will not reflect any changes and will always point to the original error stream unless changed manually.

@_set_stdout#

Synopsis:

[file: IOFile] @_set_stdout -> null

Description:

Changes the standard output stream to file. file must support writing and must not be already closed.

The STDOUT constant will not reflect any changes and will always point to the original output stream unless changed manually.

Constants#

FROM_START#

Used for move_fptr, puts the file pointer at the start of the file. The same as SEEK_SET in C.

FROM_SET#

The same as FROM_START with a more familiar name.

FROM_CUR#

Used for move_fptr, does not move the file pointer. The same as SEEK_CUR in C.

FROM_END#

Used for move_fptr, puts the file pointer at the end of the file. The same as SEEK_SET in C.

STDIN#

File object of the standard input stream, changing this constant does not change the stream used by <<<, use _set_stdin instead.

STDERR#

File object of the standard error stream, changing this constant does not change the actual error stream, use _set_stderr instead.

STDOUT#

File object of the standard output stream, changing this constant does not change the stream used by >>>, use _set_stdout instead.