GIF89a;
Mini Shell
Mini Shell
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>35.6. dl — Call C functions in shared objects — Python 2.7.5 documentation</title>
<link rel="stylesheet" href="../_static/default.css" type="text/css" />
<link rel="stylesheet" href="../_static/pygments.css" type="text/css" />
<script type="text/javascript">
var DOCUMENTATION_OPTIONS = {
URL_ROOT: '../',
VERSION: '2.7.5',
COLLAPSE_INDEX: false,
FILE_SUFFIX: '.html',
HAS_SOURCE: true
};
</script>
<script type="text/javascript" src="../_static/jquery.js"></script>
<script type="text/javascript" src="../_static/underscore.js"></script>
<script type="text/javascript" src="../_static/doctools.js"></script>
<script type="text/javascript" src="../_static/sidebar.js"></script>
<link rel="search" type="application/opensearchdescription+xml"
title="Search within Python 2.7.5 documentation"
href="../_static/opensearch.xml"/>
<link rel="author" title="About these documents" href="../about.html" />
<link rel="copyright" title="Copyright" href="../copyright.html" />
<link rel="top" title="Python 2.7.5 documentation" href="../index.html" />
<link rel="up" title="35. Unix Specific Services" href="unix.html" />
<link rel="next" title="35.7. termios — POSIX style tty control" href="termios.html" />
<link rel="prev" title="35.5. crypt — Function to check Unix passwords" href="crypt.html" />
<link rel="shortcut icon" type="image/png" href="../_static/py.png" />
<script type="text/javascript" src="../_static/copybutton.js"></script>
</head>
<body>
<div class="related">
<h3>Navigation</h3>
<ul>
<li class="right" style="margin-right: 10px">
<a href="../genindex.html" title="General Index"
accesskey="I">index</a></li>
<li class="right" >
<a href="../py-modindex.html" title="Python Module Index"
>modules</a> |</li>
<li class="right" >
<a href="termios.html" title="35.7. termios — POSIX style tty control"
accesskey="N">next</a> |</li>
<li class="right" >
<a href="crypt.html" title="35.5. crypt — Function to check Unix passwords"
accesskey="P">previous</a> |</li>
<li><img src="../_static/py.png" alt=""
style="vertical-align: middle; margin-top: -1px"/></li>
<li><a href="http://www.python.org/">Python</a> »</li>
<li>
<a href="../index.html">Python 2.7.5 documentation</a> »
</li>
<li><a href="index.html" >The Python Standard Library</a> »</li>
<li><a href="unix.html" accesskey="U">35. Unix Specific Services</a> »</li>
</ul>
</div>
<div class="document">
<div class="documentwrapper">
<div class="bodywrapper">
<div class="body">
<div class="section" id="module-dl">
<span id="dl-call-c-functions-in-shared-objects"></span><h1>35.6. <a class="reference internal" href="#module-dl" title="dl: Call C functions in shared objects. (deprecated) (Unix)"><tt class="xref py py-mod docutils literal"><span class="pre">dl</span></tt></a> — Call C functions in shared objects<a class="headerlink" href="#module-dl" title="Permalink to this headline">¶</a></h1>
<p class="deprecated">
<span class="versionmodified">Deprecated since version 2.6: </span>The <a class="reference internal" href="#module-dl" title="dl: Call C functions in shared objects. (deprecated) (Unix)"><tt class="xref py py-mod docutils literal"><span class="pre">dl</span></tt></a> module has been removed in Python 3. Use the <a class="reference internal" href="ctypes.html#module-ctypes" title="ctypes: A foreign function library for Python."><tt class="xref py py-mod docutils literal"><span class="pre">ctypes</span></tt></a>
module instead.</p>
<p>The <a class="reference internal" href="#module-dl" title="dl: Call C functions in shared objects. (deprecated) (Unix)"><tt class="xref py py-mod docutils literal"><span class="pre">dl</span></tt></a> module defines an interface to the <tt class="xref c c-func docutils literal"><span class="pre">dlopen()</span></tt> 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.</p>
<div class="admonition warning">
<p class="first admonition-title">Warning</p>
<p class="last">The <a class="reference internal" href="#module-dl" title="dl: Call C functions in shared objects. (deprecated) (Unix)"><tt class="xref py py-mod docutils literal"><span class="pre">dl</span></tt></a> module bypasses the Python type system and error handling. If
used incorrectly it may cause segmentation faults, crashes or other incorrect
behaviour.</p>
</div>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">This module will not work unless <tt class="docutils literal"><span class="pre">sizeof(int)</span> <span class="pre">==</span> <span class="pre">sizeof(long)</span> <span class="pre">==</span> <span class="pre">sizeof(char</span>
<span class="pre">*)</span></tt> If this is not the case, <a class="reference internal" href="exceptions.html#exceptions.SystemError" title="exceptions.SystemError"><tt class="xref py py-exc docutils literal"><span class="pre">SystemError</span></tt></a> will be raised on import.</p>
</div>
<p>The <a class="reference internal" href="#module-dl" title="dl: Call C functions in shared objects. (deprecated) (Unix)"><tt class="xref py py-mod docutils literal"><span class="pre">dl</span></tt></a> module defines the following function:</p>
<dl class="function">
<dt id="dl.open">
<tt class="descclassname">dl.</tt><tt class="descname">open</tt><big>(</big><em>name</em><span class="optional">[</span>, <em>mode=RTLD_LAZY</em><span class="optional">]</span><big>)</big><a class="headerlink" href="#dl.open" title="Permalink to this definition">¶</a></dt>
<dd><p>Open a shared object file, and return a handle. Mode signifies late binding
(<a class="reference internal" href="#dl.RTLD_LAZY" title="dl.RTLD_LAZY"><tt class="xref py py-const docutils literal"><span class="pre">RTLD_LAZY</span></tt></a>) or immediate binding (<a class="reference internal" href="#dl.RTLD_NOW" title="dl.RTLD_NOW"><tt class="xref py py-const docutils literal"><span class="pre">RTLD_NOW</span></tt></a>). Default is
<a class="reference internal" href="#dl.RTLD_LAZY" title="dl.RTLD_LAZY"><tt class="xref py py-const docutils literal"><span class="pre">RTLD_LAZY</span></tt></a>. Note that some systems do not support <a class="reference internal" href="#dl.RTLD_NOW" title="dl.RTLD_NOW"><tt class="xref py py-const docutils literal"><span class="pre">RTLD_NOW</span></tt></a>.</p>
<p>Return value is a <tt class="xref py py-class docutils literal"><span class="pre">dlobject</span></tt>.</p>
</dd></dl>
<p>The <a class="reference internal" href="#module-dl" title="dl: Call C functions in shared objects. (deprecated) (Unix)"><tt class="xref py py-mod docutils literal"><span class="pre">dl</span></tt></a> module defines the following constants:</p>
<dl class="data">
<dt id="dl.RTLD_LAZY">
<tt class="descclassname">dl.</tt><tt class="descname">RTLD_LAZY</tt><a class="headerlink" href="#dl.RTLD_LAZY" title="Permalink to this definition">¶</a></dt>
<dd><p>Useful as an argument to <a class="reference internal" href="#dl.open" title="dl.open"><tt class="xref py py-func docutils literal"><span class="pre">open()</span></tt></a>.</p>
</dd></dl>
<dl class="data">
<dt id="dl.RTLD_NOW">
<tt class="descclassname">dl.</tt><tt class="descname">RTLD_NOW</tt><a class="headerlink" href="#dl.RTLD_NOW" title="Permalink to this definition">¶</a></dt>
<dd><p>Useful as an argument to <a class="reference internal" href="#dl.open" title="dl.open"><tt class="xref py py-func docutils literal"><span class="pre">open()</span></tt></a>. Note that on systems which do not
support immediate binding, this constant will not appear in the module. For
maximum portability, use <a class="reference internal" href="functions.html#hasattr" title="hasattr"><tt class="xref py py-func docutils literal"><span class="pre">hasattr()</span></tt></a> to determine if the system supports
immediate binding.</p>
</dd></dl>
<p>The <a class="reference internal" href="#module-dl" title="dl: Call C functions in shared objects. (deprecated) (Unix)"><tt class="xref py py-mod docutils literal"><span class="pre">dl</span></tt></a> module defines the following exception:</p>
<dl class="exception">
<dt id="dl.error">
<em class="property">exception </em><tt class="descclassname">dl.</tt><tt class="descname">error</tt><a class="headerlink" href="#dl.error" title="Permalink to this definition">¶</a></dt>
<dd><p>Exception raised when an error has occurred inside the dynamic loading and
linking routines.</p>
</dd></dl>
<p>Example:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">dl</span><span class="o">,</span> <span class="nn">time</span>
<span class="gp">>>> </span><span class="n">a</span><span class="o">=</span><span class="n">dl</span><span class="o">.</span><span class="n">open</span><span class="p">(</span><span class="s">'/lib/libc.so.6'</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">a</span><span class="o">.</span><span class="n">call</span><span class="p">(</span><span class="s">'time'</span><span class="p">),</span> <span class="n">time</span><span class="o">.</span><span class="n">time</span><span class="p">()</span>
<span class="go">(929723914, 929723914.498)</span>
</pre></div>
</div>
<p>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.</p>
<div class="section" id="dl-objects">
<span id="id1"></span><h2>35.6.1. Dl Objects<a class="headerlink" href="#dl-objects" title="Permalink to this headline">¶</a></h2>
<p>Dl objects, as returned by <a class="reference internal" href="#dl.open" title="dl.open"><tt class="xref py py-func docutils literal"><span class="pre">open()</span></tt></a> above, have the following methods:</p>
<dl class="method">
<dt id="dl.dl.close">
<tt class="descclassname">dl.</tt><tt class="descname">close</tt><big>(</big><big>)</big><a class="headerlink" href="#dl.dl.close" title="Permalink to this definition">¶</a></dt>
<dd><p>Free all resources, except the memory.</p>
</dd></dl>
<dl class="method">
<dt id="dl.dl.sym">
<tt class="descclassname">dl.</tt><tt class="descname">sym</tt><big>(</big><em>name</em><big>)</big><a class="headerlink" href="#dl.dl.sym" title="Permalink to this definition">¶</a></dt>
<dd><p>Return the pointer for the function named <em>name</em>, as a number, if it exists in
the referenced shared object, otherwise <tt class="docutils literal"><span class="pre">None</span></tt>. This is useful in code like:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="k">if</span> <span class="n">a</span><span class="o">.</span><span class="n">sym</span><span class="p">(</span><span class="s">'time'</span><span class="p">):</span>
<span class="gp">... </span> <span class="n">a</span><span class="o">.</span><span class="n">call</span><span class="p">(</span><span class="s">'time'</span><span class="p">)</span>
<span class="gp">... </span><span class="k">else</span><span class="p">:</span>
<span class="gp">... </span> <span class="n">time</span><span class="o">.</span><span class="n">time</span><span class="p">()</span>
</pre></div>
</div>
<p>(Note that this function will return a non-zero number, as zero is the <em>NULL</em>
pointer)</p>
</dd></dl>
<dl class="method">
<dt id="dl.dl.call">
<tt class="descclassname">dl.</tt><tt class="descname">call</tt><big>(</big><em>name</em><span class="optional">[</span>, <em>arg1</em><span class="optional">[</span>, <em>arg2...</em><span class="optional">]</span><span class="optional">]</span><big>)</big><a class="headerlink" href="#dl.dl.call" title="Permalink to this definition">¶</a></dt>
<dd><p>Call the function named <em>name</em> 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 <tt class="docutils literal"><span class="pre">None</span></tt>, which will be passed as <em>NULL</em>.
Note that strings should only be passed to functions as <tt class="xref c c-type docutils literal"><span class="pre">const</span> <span class="pre">char*</span></tt>,
as Python will not like its string mutated.</p>
<p>There must be at most 10 arguments, and arguments not given will be treated as
<tt class="docutils literal"><span class="pre">None</span></tt>. The function’s return value must be a C <tt class="xref c c-type docutils literal"><span class="pre">long</span></tt>, which is a
Python integer.</p>
</dd></dl>
</div>
</div>
</div>
</div>
</div>
<div class="sphinxsidebar">
<div class="sphinxsidebarwrapper">
<h3><a href="../contents.html">Table Of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">35.6. <tt class="docutils literal"><span class="pre">dl</span></tt> — Call C functions in shared objects</a><ul>
<li><a class="reference internal" href="#dl-objects">35.6.1. Dl Objects</a></li>
</ul>
</li>
</ul>
<h4>Previous topic</h4>
<p class="topless"><a href="crypt.html"
title="previous chapter">35.5. <tt class="docutils literal"><span class="pre">crypt</span></tt> — Function to check Unix passwords</a></p>
<h4>Next topic</h4>
<p class="topless"><a href="termios.html"
title="next chapter">35.7. <tt class="docutils literal"><span class="pre">termios</span></tt> — POSIX style tty control</a></p>
<h3>This Page</h3>
<ul class="this-page-menu">
<li><a href="../bugs.html">Report a Bug</a></li>
<li><a href="../_sources/library/dl.txt"
rel="nofollow">Show Source</a></li>
</ul>
<div id="searchbox" style="display: none">
<h3>Quick search</h3>
<form class="search" action="../search.html" method="get">
<input type="text" name="q" />
<input type="submit" value="Go" />
<input type="hidden" name="check_keywords" value="yes" />
<input type="hidden" name="area" value="default" />
</form>
<p class="searchtip" style="font-size: 90%">
Enter search terms or a module, class or function name.
</p>
</div>
<script type="text/javascript">$('#searchbox').show(0);</script>
</div>
</div>
<div class="clearer"></div>
</div>
<div class="related">
<h3>Navigation</h3>
<ul>
<li class="right" style="margin-right: 10px">
<a href="../genindex.html" title="General Index"
>index</a></li>
<li class="right" >
<a href="../py-modindex.html" title="Python Module Index"
>modules</a> |</li>
<li class="right" >
<a href="termios.html" title="35.7. termios — POSIX style tty control"
>next</a> |</li>
<li class="right" >
<a href="crypt.html" title="35.5. crypt — Function to check Unix passwords"
>previous</a> |</li>
<li><img src="../_static/py.png" alt=""
style="vertical-align: middle; margin-top: -1px"/></li>
<li><a href="http://www.python.org/">Python</a> »</li>
<li>
<a href="../index.html">Python 2.7.5 documentation</a> »
</li>
<li><a href="index.html" >The Python Standard Library</a> »</li>
<li><a href="unix.html" >35. Unix Specific Services</a> »</li>
</ul>
</div>
<div class="footer">
© <a href="../copyright.html">Copyright</a> 1990-2019, Python Software Foundation.
<br />
The Python Software Foundation is a non-profit corporation.
<a href="http://www.python.org/psf/donations/">Please donate.</a>
<br />
Last updated on Jul 03, 2019.
<a href="../bugs.html">Found a bug</a>?
<br />
Created using <a href="http://sphinx.pocoo.org/">Sphinx</a> 1.1.3.
</div>
</body>
</html>
./BlackJoker Mini Shell 1.0