<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <html> <head> <link rel="STYLESHEET" href="modpython.css" type='text/css' /> <link rel="first" href="modpython.html" title='Mod_python Manual' /> <link rel='contents' href='contents.html' title="Contents" /> <link rel='index' href='genindex.html' title='Index' /> <link rel='last' href='about.html' title='About this document...' /> <link rel='help' href='about.html' title='About this document...' /> <link rel="prev" href="hand-psp.html" /> <link rel="parent" href="handlers.html" /> <link rel="next" href="security.html" /> <meta name='aesop' content='information' /> <title>7.3 CGI Handler</title> </head> <body> <DIV CLASS="navigation"> <div id='top-navigation-panel' xml:id='top-navigation-panel'> <table align="center" width="100%" cellpadding="0" cellspacing="2"> <tr> <td class='online-navigation'><a rel="prev" title="7.2 PSP Handler" href="hand-psp.html"><img src='previous.png' border='0' height='32' alt='Previous Page' width='32' /></A></td> <td class='online-navigation'><a rel="parent" title="7. 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Security</A> </div> <hr /></div> </DIV> <!--End of Navigation Panel--> <H1><A NAME="SECTION009300000000000000000"></A><A NAME="hand-cgi"></A> <BR> 7.3 CGI Handler </H1> <P> <a id='l2h-296' xml:id='l2h-296'></a> <P> CGI handler is a handler that emulates the CGI environment under mod_python. <P> Note that this is not a "<tt class="samp">true</tt>" CGI environment in that it is emulated at the Python level. <code>stdin</code> and <code>stdout</code> are provided by substituting <code>sys.stdin</code> and <code>sys.stdout</code>, and the environment is replaced by a dictionary. The implication is that any outside programs called from within this environment via <code>os.system</code>, etc. will not see the environment available to the Python program, nor will they be able to read/write from standard input/output with the results expected in a "<tt class="samp">true</tt>" CGI environment. <P> The handler is provided as a stepping stone for the migration of legacy code away from CGI. It is not recommended that you settle on using this handler as the preferred way to use mod_python for the long term. This is because the CGI environment was not intended for execution within threads (e.g. requires changing of current directory with is inherently not thread-safe, so to overcome this cgihandler maintains a thread lock which forces it to process one request at a time in a multi-threaded server) and therefore can only be implemented in a way that defeats many of the advantages of using mod_python in the first place. <P> To use it, simply add this to your <span class="file">.htaccess</span> file: <P> <div class="verbatim"><pre> SetHandler mod_python PythonHandler mod_python.cgihandler </pre></div> <P> As of version 2.7, the cgihandler will properly reload even indirectly imported module. This is done by saving a list of loaded modules (sys.modules) prior to executing a CGI script, and then comparing it with a list of imported modules after the CGI script is done. Modules (except for whose whose __file__ attribute points to the standard Python library location) will be deleted from sys.modules thereby forcing Python to load them again next time the CGI script imports them. <P> If you do not want the above behavior, edit the <span class="file">cgihandler.py</span> file and comment out the code delimited by ###. <P> Tests show the cgihandler leaking some memory when processing a lot of file uploads. It is still not clear what causes this. The way to work around this is to set the Apache <code>MaxRequestsPerChild</code> to a non-zero value. <P> <DIV CLASS="navigation"> <div class='online-navigation'> <p></p><hr /> <table align="center" width="100%" cellpadding="0" cellspacing="2"> <tr> <td class='online-navigation'><a rel="prev" title="7.2 PSP Handler" href="hand-psp.html"><img src='previous.png' border='0' height='32' alt='Previous Page' width='32' /></A></td> <td class='online-navigation'><a rel="parent" title="7. 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Security</A> </div> </div> <hr /> <span class="release-info">Release 3.3.1, documentation updated on January 29, 2007.</span> </DIV> <!--End of Navigation Panel--> </BODY> </HTML>