16.6 dl -- Call C functions in shared objects

16.6 `dl` -- Call C functions in shared objects

Availability: Unix.

The dl module defines an interface to the dlopen() function, which is the most common interface on Unix platforms for handling dynamically linked libraries. It allows the program to call arbitrary functions in such a library.

Warning: The dl module bypasses the Python type system and error handling. If used incorrectly it may cause segmentation faults, crashes or other incorrect behaviour.

Note: This module will not work unless sizeof(int) == sizeof(long) == sizeof(char *) If this is not the case, SystemError will be raised on import.

The dl module defines the following function:

open( name[, mode = RTLD_LAZY]): Open a shared object file, and return a handle. Mode signifies late binding (RTLD_LAZY) or immediate binding (RTLD_NOW). Default is RTLD_LAZY. Note that some systems do not support RTLD_NOW.
Return value is a dlobject.

The dl module defines the following constants:

RTLD_LAZY: Useful as an argument to open().

RTLD_NOW: Useful as an argument to open(). Note that on systems which do not support immediate binding, this constant will not appear in the module. For maximum portability, use hasattr() to determine if the system supports immediate binding.

The dl module defines the following exception:

exception error: Exception raised when an error has occurred inside the dynamic loading and linking routines.

Example:

>>> import dl, time
>>> a=dl.open('/lib/libc.so.6')
>>> a.call('time'), time.time()
(929723914, 929723914.498)

This example was tried on a Debian GNU/Linux system, and is a good example of the fact that using this module is usually a bad alternative.

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