Web server features

A. Server-side include and CGI

With the Apache web server software, these special commands are activated only if they are in a file whose name has .shtml at the end (i.e., as an extension). Otherwise Apache doesn't know to look at the HTML; it just passes it along and doesn't notice these.

Server-side include

To include the file little_bit.html into an HTML file myfile.shtml, in this second file put a line

<!--#include file="little_bit.html"-->

at the place you want.

Sample use: If you have lots of HTML pages where you want your name and email address at the end, you could put those in a file contact_info.html and then include that into the other files. You'd have to name the other files with .shtml .

Server-side CGI

To run a CGI program little.cgi and include the output as just one part of an HTML file myfile.shtml, in this file put a line

<!--#exec cgi="little.cgi"-->

The program little.cgi should start its output with

print "Content-type: text/html\n\n";

(Note the extra blank line as usual). However, your CGI program doesn't need to output title information and tags, so don't use
CGI_Header.

Sample use: If you want to put an access counter on your home page, do this:

Step 1. If your home page is now index.html rename it index.shtml

Step 2. In the HTML for your home page, put a line

<!--#exec cgi="count.cgi"-->

where you want the count to appear.

Step 3. Write the counter script count.cgi to output only the
Content-type: line, a blank line, and HTML giving the count, for example

print "Content-type: text/html\n\n";
<HR> There have been 51 visitors to this page. <HR>

Remember <HR> is for Horizontal Rule, which seems nice for this message, or else you could omit <HR> and end the line with <BR> instead. Your script will have a print statement such as

print "<HR>There have been $count visitors to this page.<HR>\n";

OR you can put everything that doesn't change in your home page, so that Step 2 has

<HR>
There have been <!--#exec cgi="count.cgi"--> visitors to this page.
<HR>

and Step 3 (your CGI script) has simply

print "Content-type: text/html\n\n";
print "$count\n";

B. Server redirect

Usually a CGI script produces a Content-type: ... line followed by a blank line and HTML. What the HTML says probably depends partly on information computed in the script.

What if you want your CGI script always to produce the same HTML, for example HTML that simply has a thank-you message that is the same every time?

Here is how to do that:

Step 1. Make a file thanks.html that has your message.

Step 2. Write your CGI script to output only this:

Location: thanks.html followed by a blank line.

In other words, in your script use

print "Location: thanks.html\n\n";

That's all. This is called ``server redirect'' because the server starts out thinking it might get an HTML page but when it sees the Location: information instead of Content-type: it just goes to that page.