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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<title>ActivePerl FAQ - Web Programming</title>
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<h1>Web Programming (CGI and PerlIS)</h1>
<ul>
<li><a class="doc" href="#NAME">NAME</a></li>
<li><a class="doc" href="#DESCRIPTION">DESCRIPTION</a>
<ul>
<li><a class="doc" href="#What_is_HTTP_and_how_do_I_get_m">What is HTTP, and how do I
get more information on it?</a></li>
<li><a class="doc" href="#What_is_CGI_and_how_do_I_get_mo">What is CGI, and how do I
get more information on it?</a></li>
<li><a class="doc" href="#How_do_I_return_a_graphics_file_">How do I return a graphics
file from a CGI script?</a></li>
<li><a class="doc" href="#My_CGI_scripts_don_t_seem_to_run">My CGI scripts don't seem
to run right under PerlIS.</a></li>
<li><a class="doc" href="#How_does_my_script_know_if_it_s_">How does my script know if
it's running under ActivePerl or</a></li>
<li><a class="doc" href="#What_CGI_modules_run_with_Perl_f">What CGI modules run with
ActivePerl?</a></li>
<li><a class="doc" href="#How_do_I_use_redirection_in_my_s">How do I use redirection
in my script?</a></li>
<li><a class="doc" href="#What_are_cookies_and_how_do_I_us">What are cookies and how
do I use them?</a></li>
<li><a class="doc" href="#How_do_I_get_the_e_mail_address_">How do I get the e-mail
address of the user?</a></li>
<li><a class="doc" href="#I_need_a_CGI_script_to_do_a_cert">I need a CGI script to do
a certain task. Has anyone done it before?</a></li>
<li><a class="doc" href="#How_do_I_test_my_CGI_programs_th">How do I test my CGI
programs that take arguments without running</a></li>
<li><a class="doc" href="#The_Content_Type_header_field_I">The Content-Type: header
field I output from my CGI script shows up</a></li>
<li><a class="doc" href="#When_I_try_to_run_a_CGI_script_f">When I try to run a CGI
script from my browser, it tries to</a></li>
<!-- <li><a class="doc" href="#What_s_Perl_for_WSAPI_">What's Perl for WSAPI?</a></li> -->
</ul>
</li>
<li><a class="doc" href="#AUTHOR_AND_COPYRIGHT">AUTHOR AND COPYRIGHT</a></li>
</ul>
<h2><a name="NAME">NAME</a></h2>
<p>ActivePerl-faq7 - Web Programming (CGI and PerlIS)</p>
<h2><a name="DESCRIPTION">DESCRIPTION</a></h2>
<p>Web development with ActivePerl</p>
<h2><a name="What_is_HTTP_and_how_do_I_get_m">What is HTTP, and how do I get
more information on it?</a></h2>
<p>HTTP (HyperText Transfer Protocol) is the protocol that web browsers use to
talk to web servers. The official specification for the HTTP standard is
available on the W3 Consortium web server at:</p>
<pre>
<a class="doc" href="http://www.w3.org/pub/WWW/Protocols/">http://www.w3.org/pub/WWW/Protocols/</a>
</pre>
<p>Some more readable introductions can be found on the Yahoo HTTP page at:</p>
<pre>
<a class="doc" href="http://www.yahoo.com/Computers_and_Internet/Internet/World_Wide_Web/HTTP/">http://www.yahoo.com/Computers_and_Internet/Internet/World_Wide_Web/HTTP/</a>
</pre>
<h2><a name="What_is_CGI_and_how_do_I_get_mo">What is CGI, and how do I get more
information on it?</a></h2>
<p>CGI (Common Gateway Interface) is a protocol used by web servers to run
server programs. Scripts that support the CGI protocol are sometimes called
``CGI scripts''; this leads to the unfortunate misperception that CGI is a
language of its own.</p>
<p>The classic information on CGI is available on the NCSA server at:</p>
<pre>
<a class="doc" href="http://hoohoo.ncsa.uiuc.edu/cgi/">http://hoohoo.ncsa.uiuc.edu/cgi/</a>
</pre>
<p>If you haven't read this, read it now. If it doesn't click for you, you can
check the Yahoo CGI page at:</p>
<pre>
<a class="doc" href="http://dir.yahoo.com/Computers_and_Internet/Software/Internet/World_Wide_Web/Servers/Server_Side_Scripting/Common_Gateway_Interface__CGI_/">http://dir.yahoo.com/Computers_and_Internet/Software/Internet/World_Wide_Web/Servers/Server_Side_Scripting/Common_Gateway_Interface__CGI_/</a>
</pre>
<p>(All one URL)</p>
<p>Try also the following URL for CGI programming in Perl:</p>
<pre>
<a class="doc" href="http://www.perl.com/CPAN-local/doc/FAQs/cgi/perl-cgi-faq.html">http://www.perl.com/CPAN-local/doc/FAQs/cgi/perl-cgi-faq.html</a>
</pre>
<p>If you still don't get it, try one of the
``get-rich-quick-by-writing-CGI-scripts'' books at your local bookstores.</p>
<h2><a name="How_do_I_return_a_graphics_file_">How do I return a graphics file
from a CGI script?</a></h2>
<p>One of the big differences between UNIX and Win32 platforms is that on Win32
there's a difference between text or ASCII files and binary file. To return a
graphics file, you need to specify that the file is a binary file, and that the
standard output stream should accept binary data. Try something like this:</p>
<pre>
$MY_FILE_NAME = 'Penelope.jpg';
$CHUNK_SIZE = 4096;
open( MY_FILE, "<$MY_FILE_NAME" )
or die( "Can't open $MY_FILE_NAME: $!\n" );
print "Content-type: image/jpeg\r\n";
print "\r\n";
binmode( MY_FILE ); # These are crucial!
binmode( STDOUT );
while ( $cb = read( MY_FILE, $data, $CHUNK_SIZE ) ) {
print $data;
}
close( MY_FILE );
</pre>
<h2><a name="My_CGI_scripts_don_t_seem_to_run">My CGI scripts don't seem to run
right under PerlIS.</a></h2>
<p>Earlier versions of Perl for ISAPI did not output headers correctly, and this
caused Perl for ISAPI scripts to misbehave. You could work around this in
earlier versions of PerlIS by sending the headers at the beginning of your
script like this:</p>
<pre>
print <<"END";
HTTP/1.0 200 OK
Content-Type: text/html
END
</pre>
<p>This is no longer necessary with the current version of Perl for ISAPI, as
Perl for ISAPI sends the correct headers. The Registry value that governs this
is <code>EnableCGIHeader</code>, a REG_DWORD value that is set to 1 by default.
This value is stored under the Registry key
HKEY_LOCAL_MACHINE\SOFTWARE\ActiveState\PerlIS. If you need to turn off the
automatic generation of the header, set this value to 0.</p>
<h2><a name="How_does_my_script_know_if_it_s_">How does my script know if it's
running under ActivePerl or Perl for ISAPI?</a></h2>
<p>Perl for ISAPI sets an environment variable, <code>PERLXS</code>, for scripts
that are executed under Perl for ISAPI.</p>
<pre>
my $running_under_perlis = $ENV{PERLXS} eq 'PerlIS';
</pre>
<h2><a name="How_does_my_script_know_if_it_s_">How does my script know if it's
running under ActivePerl or Perl for WebSite?</a></h2>
<p>Perl for WebSite sets an environment variable, <code>PERLXS</code>, for
scripts that are executed under Perl for WebSite.</p>
<pre>
my $running_under_perlws = $ENV{PERLXS} eq 'PerlWS';
</pre>
<h2><a name="What_CGI_modules_run_with_Perl_f">What CGI modules run with
ActivePerl?</a></h2>
<p>The <em>CGI.pm</em> module works with ActivePerl. It's included with
ActivePerl, and you can use it in your program with the statement <code>use CGI</code>.
Complete documentation for the CGI module is embedded in the module, and can be
read with <code>perldoc CGI</code>.</p>
<h2><a name="How_do_I_use_redirection_in_my_s">How do I use redirection in my
script?</a></h2>
<p>You can use redirection to point the client browser to another file or
script, usually in a way that's invisible to the user. The CGI module provides
the <code>redirect()</code> function for this purpose. The following code
redirects the client browser to <a class="doc" href="http://www.perl.com">http://www.perl.com</a>
and works with both CGI or PerlIS:</p>
<pre>
use CGI qw(:standard);
print redirect('<a class="doc" href="http://www.perl.com">http://www.perl.com</a>');
</pre>
<h2><a name="What_are_cookies_and_how_do_I_us">What are cookies and how do I use
them?</a></h2>
<p>Cookies are packets of data that a server can give to a client, such as a
browser, to maintain information even after the browser has left this site. This
can be used to to identify the client in future interactions or to store user
preferences. Cookies were first defined by Netscape, and the definition of
cookies can be found at:</p>
<pre>
<a class="doc" href="http://home.netscape.com/newsref/std/cookie_spec.html">http://home.netscape.com/newsref/std/cookie_spec.html</a>
</pre>
<p>The CGI module provides support for managing cookies. See <a class="doc" href="#What_CGI_modules_run_with_Perl_f">What
CGI modules run with ActivePerl?</a> for information about the CGI module,
including the location of online documentation.</p>
<h2><a name="How_do_I_get_the_e_mail_address_">How do I get the e-mail address
of the user?</a></h2>
<p>It's not, in general, possible to get the e-mail address of a user without
asking them for it. If you need an e-mail address, provide the user with a form
to fill in an address.</p>
<p>The HTTP specification (see <a class="doc" href="#What_is_HTTP_and_how_do_I_get_m">What
is HTTP, and how do I get more information on it?</a>) defines an HTTP request
header field, <code>From:</code>, that can contain the e-mail address of the
user making the connection. Your script can retrieve it using the environment
variable HTTP_FROM. However, it's rarely provided and can't really be counted
on.</p>
<p>There are all kinds of sneaky ways to determine where requests come from --
like checking the IP address that was used to connect -- but you can't figure
out the e-mail address of the user this way.</p>
<p>Generally, it's considered a violation of the user's privacy to get their
e-mail address without their knowledge. Perhaps that's why it's so difficult.</p>
<h2><a name="I_need_a_CGI_script_to_do_a_cert">I need a CGI script to do a
certain task. Has anyone done it before?</a></h2>
<p>There are several CGI script archives on the web. You may not be able to find
exactly the script you want, but you will probably find something that can be
adapted to your needs.</p>
<p>Two of the most famous script pages are:</p>
<ul>
<li>
<p>Jenda's pages: <a href="http://www24.brinkster.com/jenda">
www24.brinkster.com/jenda</a></p>
</li>
<li>
<p>The Perl Monks: <a href="http://www.perlmonks.org">www.perlmonks.org</a></p>
</li>
<li>
<p>Matt's script replacements: <a href="http://nms-cgi.sourceforge.net">
nms-cgi.sourceforge.net</a></p>
</li>
<li>
<p>Dave Doyle's Script Archive: <a class="doc" href="http://www.davedoyle.com/help/scripts.html">www.davedoyle.com/help/scripts.html</a></p>
</li>
</ul>
<p>Note that most script archives have UNIX-targeted scripts, and you may have
to make some adaptations to them to make them run (see <a class="doc" href="ActivePerl-Winfaq5.html#How_do_I_make_a_UNIX_based_scrip">How
do I make a UNIX-based script work?</a>).</p>
<p>This is one of the most common questions on the Perl-Win32-Users list.
Occasionally it's phrased more like "I have a program to write. Here are the
specs. Please e-mail it to me by Friday." Hopefully the reader can understand
why these messages are usually answered rudely, if they are answered at all.</p>
<h2><a name="How_do_I_test_my_CGI_programs_th">How do I test my CGI programs
that take arguments without running them through the web server?</a></h2>
<p>The hard way to test your CGI programs from the command line is to set up
environment variables and a standard input stream just like a web server would
(see the CGI 1.1 specification for more details on this -- see <a class="doc" href="#What_is_CGI_and_how_do_I_get_mo">What
is CGI, and how do I get more information on it?</a>).</p>
<p>The easy way is to use <code>CGI.pm</code>, the Perl module for CGI
programming. It provides an easy mechanism to run CGI programs, with arguments,
from the command line. See <a class="doc" href="#What_CGI_modules_run_with_Perl_f">What CGI
modules run with ActivePerl?</a>.</p>
<h2><a name="The_Content_Type_header_field_I">The Content-Type: header field I
output from my CGI script shows up in the web browser.</a></h2>
<p>You are using an older version of Perl for ISAPI as your Perl interpreter on
an IIS web server, but it's not outputting an HTTP status line. You should be
able to fix this by installing the most recent version of Perl and PerlIS. See <a class="doc" href="#My_CGI_scripts_don_t_seem_to_run">My
CGI scripts don't seem to run right under Perl for ISAPI.</a> for more details.</p>
<h2><a name="When_I_try_to_run_a_CGI_script_f">When I try to run a CGI script
from my browser, it tries to download a file of type
"application/x-perl" instead.</a></h2>
<p>Your web server has been misconfigured. It doesn't know that it should
execute your Perl program, so it's just returning it to the browser. See <a class="doc" href="ActivePerl-Winfaq6.html">the
perlwin32faq6 manpage</a> for details on how to configure your particular web
server to know that Perl scripts should be executed.</p>
<!-- <h2><a name="What_s_Perl_for_WSAPI_">What's Perl for WSAPI?</a></h2>
<p>Perl for WSAPI, or PerlWS for short, offers the same functionality as Perl
for ISAPI to users of O'Reilly's WebSite Professional web server.</p> -->
<h2><a name="AUTHOR_AND_COPYRIGHT">AUTHOR AND COPYRIGHT</a></h2>
<p>This FAQ was originally assembled and maintained by Evangelo Prodromou. It
has been revised and updated by Brian Jepson of O'Reilly & Associates, David
Grove, David Dmytryshyn and David Sparks of ActiveState.</p>
<p>This FAQ is in the public domain. If you use it, however, please ensure that
you give credit to the original authors.</p>
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