6.1.3 File Descriptor Operations

These functions operate on I/O streams referred to using file descriptors.

close (fd): Close file descriptor fd. Availability: Macintosh, Unix, Windows.
Note: this function is intended for low-level I/O and must be applied to a file descriptor as returned by open() or pipe(). To close a ``file object'' returned by the built-in function open() or by popen() or fdopen(), use its close() method.

dup (fd): Return a duplicate of file descriptor fd. Availability: Macintosh, Unix, Windows.

dup2 (fd, fd2): Duplicate file descriptor fd to fd2, closing the latter first if necessary. Availability: Unix, Windows.

fstat (fd): Return status for file descriptor fd, like stat(). Availability: Unix, Windows.

fstatvfs (fd): Return information about the filesystem containing the file associated with file descriptor fd, like statvfs(). Availability: Unix.

ftruncate (fd, length): Truncate the file corresponding to file descriptor fd, so that it is at most length bytes in size. Availability: Unix.

lseek (fd, pos, how): Set the current position of file descriptor fd to position pos, modified by how: 0 to set the position relative to the beginning of the file; 1 to set it relative to the current position; 2 to set it relative to the end of the file. Availability: Macintosh, Unix, Windows.

open (file, flags[, mode])

Open the file file and set various flags according to flags and possibly its mode according to mode. The default mode is 0777 (octal), and the current umask value is first masked out. Return the file descriptor for the newly opened file. Availability: Macintosh, Unix, Windows.

For a description of the flag and mode values, see the C run-time documentation; flag constants (like O_RDONLY and O_WRONLY) are defined in this module too (see below).

Note: this function is intended for low-level I/O. For normal usage, use the built-in function open(), which returns a ``file object'' with read() and write() methods (and many more).

pipe (): Create a pipe. Return a pair of file descriptors (r, w) usable for reading and writing, respectively. Availability: Unix, Windows.

read (fd, n): Read at most n bytes from file descriptor fd. Return a string containing the bytes read. Availability: Macintosh, Unix, Windows.
Note: this function is intended for low-level I/O and must be applied to a file descriptor as returned by open() or pipe(). To read a ``file object'' returned by the built-in function open() or by popen() or fdopen(), or sys.stdin, use its read() or readline() methods.

tcgetpgrp (fd): Return the process group associated with the terminal given by fd (an open file descriptor as returned by open()). Availability: Unix.

tcsetpgrp (fd, pg): Set the process group associated with the terminal given by fd (an open file descriptor as returned by open()) to pg. Availability: Unix.

ttyname (fd): Return a string which specifies the terminal device associated with file-descriptor fd. If fd is not associated with a terminal device, an exception is raised. Availability: Unix.

write (fd, str): Write the string str to file descriptor fd. Return the number of bytes actually written. Availability: Macintosh, Unix, Windows.
Note: this function is intended for low-level I/O and must be applied to a file descriptor as returned by open() or pipe(). To write a ``file object'' returned by the built-in function open() or by popen() or fdopen(), or sys.stdout or sys.stderr, use its write() method.

The following data items are available for use in constructing the flags parameter to the open() function.

O_RDONLY
O_WRONLY
O_RDWR
O_NDELAY
O_NONBLOCK
O_APPEND
O_DSYNC
O_RSYNC
O_SYNC
O_NOCTTY
O_CREAT
O_EXCL
O_TRUNC: Options for the flag argument to the open() function. These can be bit-wise OR'd together. Availability: Macintosh, Unix, Windows.

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