/Doc/library/dl.rst
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- :mod:`dl` --- Call C functions in shared objects
- ================================================
- .. module:: dl
- :platform: Unix
- :synopsis: Call C functions in shared objects.
- :deprecated:
- .. deprecated:: 2.6
- The :mod:`dl` module has been removed in Python 3.0. Use the :mod:`ctypes`
- module instead.
- .. sectionauthor:: Moshe Zadka <moshez@zadka.site.co.il>
- The :mod:`dl` module defines an interface to the :cfunc:`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 :mod:`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, :exc:`SystemError` will be raised on import.
- The :mod:`dl` module defines the following function:
- .. function:: open(name[, mode=RTLD_LAZY])
- Open a shared object file, and return a handle. Mode signifies late binding
- (:const:`RTLD_LAZY`) or immediate binding (:const:`RTLD_NOW`). Default is
- :const:`RTLD_LAZY`. Note that some systems do not support :const:`RTLD_NOW`.
- Return value is a :class:`dlobject`.
- The :mod:`dl` module defines the following constants:
- .. data:: RTLD_LAZY
- Useful as an argument to :func:`open`.
- .. data:: RTLD_NOW
- Useful as an argument to :func:`open`. Note that on systems which do not
- support immediate binding, this constant will not appear in the module. For
- maximum portability, use :func:`hasattr` to determine if the system supports
- immediate binding.
- The :mod:`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.
- .. _dl-objects:
- Dl Objects
- ----------
- Dl objects, as returned by :func:`open` above, have the following methods:
- .. method:: dl.close()
- Free all resources, except the memory.
- .. method:: dl.sym(name)
- Return the pointer for the function named *name*, as a number, if it exists in
- the referenced shared object, otherwise ``None``. This is useful in code like::
- >>> if a.sym('time'):
- ... a.call('time')
- ... else:
- ... time.time()
- (Note that this function will return a non-zero number, as zero is the *NULL*
- pointer)
- .. method:: dl.call(name[, arg1[, arg2...]])
- Call the function named *name* in the referenced shared object. The arguments
- must be either Python integers, which will be passed as is, Python strings, to
- which a pointer will be passed, or ``None``, which will be passed as *NULL*.
- Note that strings should only be passed to functions as :ctype:`const char\*`,
- as Python will not like its string mutated.
- There must be at most 10 arguments, and arguments not given will be treated as
- ``None``. The function's return value must be a C :ctype:`long`, which is a
- Python integer.