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 articlesA805 - Web Application Deployment - Perl - modPerl, Mason, CGI.pm and LWP 
Automating access to a page obscured behind a holding page - (2009-09-23) 
Embperl - (2005-03-28)P403 - Perl - The Common Gateway Interface 
Perl and CGI - simple form, and monitoring script. - (2011-09-17) 
Teaching examples in Perl - third and final part - (2010-06-27) 
Perl and the Common Gateway Interface - out of fashion but still very useful? - (2009-12-26) 
Handling nasty characters - Perl, PHP, Python, Tcl, Lua - (2009-06-14)
Some other Articles
Business is the predominant user of Tomcat, Perl and TclPHP - onwards and upwardsEffective fundraisingNear and far securityCGI v mod_perlSerious subjectHash of lists in PerlDo languages change?A Thousand and four wordsTake the train to training
4208 posts, page by page
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 at 50 posts per page
This is a page archived from The Horse's Mouth at
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.
Link to Ezine home page (for reading).
Link to Blogging home page (to add comments).