This module performs file control and I/O control on file descriptors. It is an interface to the fcntl() and ioctl() Unix routines. File descriptors can be obtained with the fileno() method of a file or socket object.
The module defines the following functions:
0. When present, it can either be an integer value, or a string. With the argument missing or an integer value, the return value of this function is the integer return value of the C fcntl() call. When the argument is a string it represents a binary structure, e.g. created by struct.pack(). The binary data is copied to a buffer whose address is passed to the C fcntl() call. The return value after a successful call is the contents of the buffer, converted to a string object. In case the fcntl() fails, an IOError is raised.
If the library modules FCNTL or
IOCTL are missing, you can find the
opcodes in the C include files
<sys/ioctl.h>. You can create the modules yourself with the
h2py script, found in the Tools/scripts/ directory.
Examples (all on a SVR4 compliant system):
import struct, fcntl, FCNTL file = open(...) rv = fcntl(file.fileno(), FCNTL.O_NDELAY, 1) lockdata = struct.pack('hhllhh', FCNTL.F_WRLCK, 0, 0, 0, 0, 0) rv = fcntl.fcntl(file.fileno(), FCNTL.F_SETLKW, lockdata)
Note that in the first example the return value variable
hold an integer value; in the second example it will hold a string
value. The structure lay-out for the lockdata variable is
system dependent -- therefore using the flock() call may be