| <HTML><HEAD><TITLE>Using python to create CGI scripts</TITLE></HEAD> |
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| <H1>Using python to create CGI scripts</H1> |
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| In this document we will (eventually) explain how to create Python CGI scripts |
| for use with Personal WebServer, WebStar and probably other Mac-based HTTP servers too. |
| Since CGI scripts are AppleEvent servers on the mac we will also learn |
| a little about general AppleEvent server programming and about applet |
| debugging. <p> |
| |
| <blockquote>Note that the current setup is very preliminary, and hence |
| itis probably not wise to base your strategic products on the information |
| in this document:-) In stead, play with the code here and join the |
| <a href="mailto:pythonmac-sig-request@python.org">pythonmac-sig</a>, where |
| we I would like to have a discussion on a real design for a Mac CGI framework |
| (preferrably something that will make CGI scripts portable to unix and other |
| platforms). |
| </blockquote> |
| |
| <h2>AppleEvent servers</h2> |
| |
| Since AppleEvent clients are easier to write and understand than servers |
| you should probably read the section on <a href="applescript.html">Open Scripting |
| clients in Python</a> first. <p> |
| |
| Next, let us have a look at the AE Server framework, |
| <a href="../Lib/toolbox/MiniAEFrame.py">MiniAEFrame.py</a>. |
| This file contains two classes, <code>MiniApplication</code> and <code>AEServer</code>. |
| MiniApplication is a tiny replacement for <code>FrameWork.Application</code>, |
| suitable if your application does not need windows and such. |
| |
| AEServer is a bit of glue that does part of the appleevent decoding for you. You |
| call <code>installaehandler</code> passing it the class and id (4-char strings) |
| of the event you have a handler for and the handler callback routine. When the |
| appleevent occurs your callback is called with the right arguments. For now, |
| your argument names are the 4-char values used internally by Open Scripting, |
| eventually there will be a translation similar to what the generated OSA client |
| suites provide. <p> |
| |
| You can test AEServer by double-clicking it. It will react to the standard |
| run/open/print/quit OSA commands. If it is running as a normal python script and you |
| drag a file onto the interpreter the script will tell you what event it got. <p> |
| |
| <h2>A Minimal CGI script</h2> |
| |
| To try a CGI script you will first need a http server. Apple's Personal Webserver |
| is fine, but I have also used the |
| shareware |
| <a href="http://www.stairways.com/netpresenz/">NetPresenz</a> |
| by Peter Lewis |
| (don't forget to pay if you give it more than a test run!). Install your |
| http server, and make sure that it can serve textual documents. <p> |
| |
| Next, let us have a look at our example CGI scripts. CGI scripts have to be |
| applications, so we will have to make an applet as explained in |
| <a href="example2.html">example 2</a>. Our applet code, |
| <a href="cgi/cgitest.cgi.py">cgitest.cgi.py</a> is a rather minimal <code>execfile</code> |
| statement. The reason for this is debugging: the real code is in |
| <a href="cgi/realcgitest.py">realcgitest.py</a>, and this way you do not have |
| to run mkapplet again every time you change the code. Rename realcgitest.py |
| to cgitest.cgi.py once you are satisfied that it works. <p> |
| |
| The resource file is not very special, with one exception: since we want to do |
| our own appleevent handling we don't want the Python initialization code to |
| create argc and argv for use, since this might gobble up any appleevents we are |
| interested in. For this reason we have included a 'Popt' resource that disables |
| the argv initialization. An easy way to create this resource is to drop |
| the <code>.rsrc</code> file (or the finished applet, if you like) onto |
| <code>EditPythonPrefs</code> and set the "no argv processing" option. <p> |
| |
| The code itself is actually not too complicated either. We install handlers |
| for "open application" and "quit" (stolen from the test code in MiniAEFrame) |
| and the <code>"WWW\275"/"sdoc"</code> event, the event sent on CGI execution. |
| The cgi handler pretty-prints the CGI arguments in HTML and returns the whole |
| string that is to be passed to the client. The actual parameters passed |
| are explained in <a href="http://www.biap.com/datapig/mrwheat/cgi_params.html"> |
| http://www.biap.com/datapig/mrwheat/cgi_params.html</a>. <p> |
| |
| To test the script drop <code>cgitest.cgi.py</code> onto <code>mkapplet</code>, |
| move the resulting <code>cgitest.cgi</code> to somewhere where it is reachable |
| by NetPresenz, and point your web browser towards it. Note that this assume you have |
| already renamed realcgitest.py to cgitest.cgi.py, otherwise you'll also have |
| to copy that file along. <p> |
| |
| For Apple's Personal Webserver you need to do a bit more: you have to copy the |
| cgi applet to somewhere in your "Webpages" folder and you have to tell the webserver |
| (in the control panels) that your CGI script exists. I don't understand what the various |
| types of cgi scripts mean, but experiment with them. |
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