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| 55 | <H1><A NAME="SECTION0010500000000000000000"> |
| 56 | 8.5 <tt class="module">dl</tt> -- |
| 57 | Call C functions in shared objects</A> |
| 58 | </H1> |
| 59 | <A NAME="module-dl"></A> |
| 60 | <p class="availability">Availability: <span |
| 61 | class="platform">Unix</span>.</p> |
| 62 | |
| 63 | <P> |
| 64 | The <tt class="module">dl</tt> module defines an interface to the |
| 65 | <tt class="cfunction">dlopen()</tt> function, which is the most common interface on |
| 66 | <span class="Unix">Unix</span> platforms for handling dynamically linked libraries. It allows |
| 67 | the program to call arbitrary functions in such a library. |
| 68 | |
| 69 | <P> |
| 70 | <span class="note"><b class="label">Note:</b> |
| 71 | This module will not work unless |
| 72 | <code>sizeof(int) == sizeof(long) == sizeof(char *)</code> |
| 73 | If this is not the case, <tt class="exception">SystemError</tt> will be raised on |
| 74 | import.</span> |
| 75 | |
| 76 | <P> |
| 77 | The <tt class="module">dl</tt> module defines the following function: |
| 78 | |
| 79 | <P> |
| 80 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 81 | <td><nobr><b><tt id='l2h-2988' xml:id='l2h-2988' class="function">open</tt></b>(</nobr></td> |
| 82 | <td><var>name</var><big>[</big><var>, mode<code> = RTLD_LAZY</code></var><big>]</big><var></var>)</td></tr></table></dt> |
| 83 | <dd> |
| 84 | Open a shared object file, and return a handle. Mode |
| 85 | signifies late binding (<tt class="constant">RTLD_LAZY</tt>) or immediate binding |
| 86 | (<tt class="constant">RTLD_NOW</tt>). Default is <tt class="constant">RTLD_LAZY</tt>. Note that some |
| 87 | systems do not support <tt class="constant">RTLD_NOW</tt>. |
| 88 | |
| 89 | <P> |
| 90 | Return value is a dlobject. |
| 91 | </dl> |
| 92 | |
| 93 | <P> |
| 94 | The <tt class="module">dl</tt> module defines the following constants: |
| 95 | |
| 96 | <P> |
| 97 | <dl><dt><b><tt id='l2h-2989' xml:id='l2h-2989'>RTLD_LAZY</tt></b></dt> |
| 98 | <dd> |
| 99 | Useful as an argument to <tt class="function">open()</tt>. |
| 100 | </dd></dl> |
| 101 | |
| 102 | <P> |
| 103 | <dl><dt><b><tt id='l2h-2990' xml:id='l2h-2990'>RTLD_NOW</tt></b></dt> |
| 104 | <dd> |
| 105 | Useful as an argument to <tt class="function">open()</tt>. Note that on systems |
| 106 | which do not support immediate binding, this constant will not appear |
| 107 | in the module. For maximum portability, use <tt class="function">hasattr()</tt> to |
| 108 | determine if the system supports immediate binding. |
| 109 | </dd></dl> |
| 110 | |
| 111 | <P> |
| 112 | The <tt class="module">dl</tt> module defines the following exception: |
| 113 | |
| 114 | <P> |
| 115 | <dl><dt><b><span class="typelabel">exception</span> <tt id='l2h-2991' xml:id='l2h-2991' class="exception">error</tt></b></dt> |
| 116 | <dd> |
| 117 | Exception raised when an error has occurred inside the dynamic loading |
| 118 | and linking routines. |
| 119 | </dd></dl> |
| 120 | |
| 121 | <P> |
| 122 | Example: |
| 123 | |
| 124 | <P> |
| 125 | <div class="verbatim"><pre> |
| 126 | >>> import dl, time |
| 127 | >>> a=dl.open('/lib/libc.so.6') |
| 128 | >>> a.call('time'), time.time() |
| 129 | (929723914, 929723914.498) |
| 130 | </pre></div> |
| 131 | |
| 132 | <P> |
| 133 | This example was tried on a Debian GNU/Linux system, and is a good |
| 134 | example of the fact that using this module is usually a bad alternative. |
| 135 | |
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| 183 | <span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span> |
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