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<title>8.5 dl -- Call C functions in shared objects
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<H1><A NAME=
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8.5 <tt class=
"module">dl
</tt> --
Call C functions in shared objects
</A>
<p class=
"availability">Availability:
<span
class=
"platform">Unix
</span>.
</p>
The
<tt class=
"module">dl
</tt> module defines an interface to the
<tt class=
"cfunction">dlopen()
</tt> function, which is the most common interface on
<span class=
"Unix">Unix
</span> platforms for handling dynamically linked libraries. It allows
the program to call arbitrary functions in such a library.
<span class=
"note"><b class=
"label">Note:
</b>
This module will not work unless
<code>sizeof(int) == sizeof(long) == sizeof(char *)
</code>
If this is not the case,
<tt class=
"exception">SystemError
</tt> will be raised on
The
<tt class=
"module">dl
</tt> module defines the following function:
<dl><dt><table cellpadding=
"0" cellspacing=
"0"><tr valign=
"baseline">
<td><nobr><b><tt id='l2h-
2988' xml:id='l2h-
2988'
class=
"function">open
</tt></b>(
</nobr></td>
<td><var>name
</var><big>[
</big><var>, mode
<code> = RTLD_LAZY
</code></var><big>]
</big><var></var>)
</td></tr></table></dt>
Open a shared object file, and return a handle. Mode
signifies late binding (
<tt class=
"constant">RTLD_LAZY
</tt>) or immediate binding
(
<tt class=
"constant">RTLD_NOW
</tt>). Default is
<tt class=
"constant">RTLD_LAZY
</tt>. Note that some
systems do not support
<tt class=
"constant">RTLD_NOW
</tt>.
Return value is a dlobject.
The
<tt class=
"module">dl
</tt> module defines the following constants:
<dl><dt><b><tt id='l2h-
2989' xml:id='l2h-
2989'
>RTLD_LAZY
</tt></b></dt>
Useful as an argument to
<tt class=
"function">open()
</tt>.
<dl><dt><b><tt id='l2h-
2990' xml:id='l2h-
2990'
>RTLD_NOW
</tt></b></dt>
Useful as an argument to
<tt class=
"function">open()
</tt>. Note that on systems
which do not support immediate binding, this constant will not appear
in the module. For maximum portability, use
<tt class=
"function">hasattr()
</tt> to
determine if the system supports immediate binding.
The
<tt class=
"module">dl
</tt> module defines the following exception:
<dl><dt><b><span class=
"typelabel">exception
</span> <tt id='l2h-
2991' xml:id='l2h-
2991'
class=
"exception">error
</tt></b></dt>
Exception raised when an error has occurred inside the dynamic loading
<div class=
"verbatim"><pre>
>>> 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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<span class=
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2.4.2, documentation updated on
28 September
2005.
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