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Training, Open Source Programming Languages This is page http://www.wellho.net/mouth/45_CGI-v-mod-perl.html Our email: info@wellho.net • Phone: 01144 1225 708225 |
| For 2023 (and 2024 ...) - we are now fully retired from IT training. We have made many, many friends over 25 years of teaching about Python, Tcl, Perl, PHP, Lua, Java, C and C++ - and MySQL, Linux and Solaris/SunOS too. Our training notes are now very much out of date, but due to upward compatability most of our examples remain operational and even relevant ad you are welcome to make us if them "as seen" and at your own risk. Lisa and I (Graham) now live in what was our training centre in Melksham - happy to meet with former delegates here - but do check ahead before coming round. We are far from inactive - rather, enjoying the times that we are retired but still healthy enough in mind and body to be active! I am also active in many other area and still look after a lot of web sites - you can find an index ((here)) |
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CGI v mod_perl
Just debunking a couple of myths today ... CGI (Common Gateway Interface) scripts are run on a web server computer under the control of a piece of web server software (typically Apache httpd), but as separate processes. This means that each time a script is called up, it has to be translated from the script language into something that can be run through compilers / interpreters depending on the language involved. Also a separate process is started on each invocation. This is all very well and good for a script that's not run very often, but if you've got a script that you expect to be run many times per minute, the constant recompiling may have a significant effect on resources. mod_perl is the Perl interpreter built into the Apache httpd server. No separate process to be started, and no re-compile each time a server side script is run, so much more efficient. Once a script has been run, it stays as part of the httpd web server. As the name kinda-implies, mod_perl scripts must be in Perl whereas CGI scripts can be in any scripting language (yes, the is a mod_python too). Since mod_perl scripts are not recompiled and re-initialised, you should ensure that all variables in them are specifically initialised rather than being assumed to be empty / zero, which is an assumption you can make with a Perl CGI script. However - a word of caution; you are likely to be running multiple processes as part of httpd each of which will have its own copy of your scripts, so you cannot assume that a variable left after one run of a mod_perl script will retain that value when the next person calls it up. More details covered, of course, on our Perl on the Web course. (written 2004-09-11, updated 2008-05-10) Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles P403 - Perl - The Common Gateway Interface[2238] Handling nasty characters - Perl, PHP, Python, Tcl, Lua - (2009-06-14) [2551] Perl and the Common Gateway Interface - out of fashion but still very useful? - (2009-12-26) [2834] Teaching examples in Perl - third and final part - (2010-06-27) [3445] Perl and CGI - simple form, and monitoring script. - (2011-09-17) A805 - Web Application Deployment - Perl - modPerl, Mason, CGI.pm and LWP [260] Embperl - (2005-03-28) [2416] Automating access to a page obscured behind a holding page - (2009-09-23)
Some other Articles
Business is the predominant user of Tomcat, Perl and TclPHP - onwards and upwards Effective fundraising Near and far security CGI v mod_perl Serious subject Hash of lists in Perl Do languages change? A Thousand and four words Take the train to training |
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Link to page ... 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96 at 50 posts per pageThis is a page archived from The Horse's Mouth at http://www.wellho.net/horse/ - the diary and writings of Graham Ellis. Every attempt was made to provide current information at the time the page was written, but things do move forward in our business - new software releases, price changes, new techniques. Please check back via our main site for current courses, prices, versions, etc - any mention of a price in "The Horse's Mouth" cannot be taken as an offer to supply at that price.
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