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1.4 CGI to mod_perl

14.02.2006

← 1.3 Manually Parsing CGI key pairs [  up  ] - [ top ] 2 LWP →

As the README and other mod_perl documents explain, mod_perl as a CGI replacement is only a small piece of what the package offers. However, it is the most popular use of mod_perl, this document is here so you can cut to the chase.

CONFIGURATION

For using mod_perl as a CGI replacement, the recommended configuration is as follows:

Alias /perl/  /real/path/to/perl-scripts/

<Location /perl>
	SetHandler  perl-script
	PerlHandler Apache::Registry
	Options +ExecCGI
</Location>

`Location' refers to the uri, not a directory, think of the above as <Location http://www.yourname.com/perl>

Any files under that location (which live on your filesystem under /real/path/to/perl-scripts/), will be handled by the Apache::Registry module, which emulates the CGI environment. The file must exist and be exe- cutable, in addition, 'Options ExecCGI' must be turned on. If you wish to have mod_perl execute scripts in any location based on file extension, use a configuration like so:

<Files ~ "\.pl$">
	SetHandler perl-script
	PerlHandler Apache::Registry
	Options ExecCGI
</Files>
Note that `ScriptAlias' does _not_ work for mod_perl.

PORTING CGI SCRIPTS

I/O If you are using Perl 5.004 most CGI scripts can run under mod_perl untouched. If you're using 5.003, Perl's built-in "read()" and "print()" functions do not work as they do under CGI. If you're using CGI.pm, use "$query-"print> instead of plain 'ol "print()".

HEADERS

By default, mod_perl does not send any headers by itself, however, you may wish to change this: PerlSendHeader On Now the response line and common headers will be sent as they are by mod_cgi. And, just as with mod_cgi, PerlSendHeader will not send a terminating newline, your script must send that itself, e.g.: print "Content-type: text/html\n\n"; If you're using CGI.pm and 'print $q->header' you do _not_ need "PerlSendHeader On".

NPH SCRIPTS

To run a CGI `nph' script under mod_perl, simply add to your code: local $| = 1; If you normally set PerlSendHeader On, add this to your httpd.conf:

<Files */nph-*> PerlSendHeader Off </Files>

PROGRAMMING PRACTICE

CGI lets you get away with sloppy programming, mod_perl does not. Why? CGI scripts have the lifetime of a single HTTP request as a separate process. When the request is over, the process goes away and everything is cleaned up for you, e.g. globals variables, open files, etc. Scripts running under mod_perl have a longer lifetime, over several request, different scripts may be in the same process. This means you must clean up after yourself. You've heard: always 'use strict' and C<-w>!!! It's more important under mod_perl Perl than anywhere else, while it's not required, it strongly recom- mended, it will save you more time in the long run. And, of course, clean scripts will still run under CGI!

TRAPS See the mod_perl_traps manpage.

SEE ALSO Apache::PerlRun(3)

ENVIRONMENT

Under CGI the Perl hash "%ENV" is magical in that it inherits environment variables from the parent process and will set them should a process spawn a child. However, with mod_perl we're in the parent process that would normally setup the common environment variables before spawning a CGI process. Therefore, mod_perl must feed these variables to "%ENV" directly. Normally, this does not happen until the response stage of a request when "PerlHandler" is called. If you wish to set variables that will be available before then, such as for a "Per- lAuthenHandler", you may use the "PerlSetEnv" configuration directive:

PerlSetEnv SomeKey SomeValue

You may also use the "PerlPassEnv" directive to pass an already existing environment variable to Perl's "%ENV":

PerlPassEnv SomeKey

The Apache::Include module makes it simple to include Apache::Registry scripts with the mod_include perl directive.

Example:
        <!--#perl sub="Apache::Include" arg="/perl/ssi.pl" -->

Other ways of mod_perl Server-side Includes

use Apache::Include ();
print "Content-type: text/html\n\n";
print "before include\n";
my $uri = "/perl/env.pl";
Apache::Include->virtual($uri);
print "after include\n";

Save this script above as ssi.pl

-> http://infocopter.homelinux.org/perl/ssi.pl

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