The #exec Command

There are occasions when SSI includes and SSI variables cannot achieve the dynamic content you want, but you still don't want to go to the trouble of writing a CGI program to generate the entire page content. By using the #exec command, you can include the output of a program within your HTML pages.

The #exec command is followed by the cgi parameter, and a valid CGI program as the attribute.

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

Simple Example: A CGI to Display Machine Load

To prove that your server machine is capable, you might want to include a load meter on the machine spec page. The page contains a lot of information and is updated frequently so you don't want a CGI program to generate the complete HTML code. The examples below will obtain the load average of the machine, then determine what colour to display the text.

The .shtml file:

<html>
 <head><title>SSI Test</title>
  <meta http-equiv="Refresh" content="2; test.shtml">
 </head>
 <body>
  This is a big page about our large machine. <p>
  <!--#exec cgi="load.cgi"-->
 </body>
</html>

The CGI Program:

#!/usr/bin/perl
 
use strict;
 
print( STDOUT "Content-type: text/html", "\n\n" );
 
my $uptime = `uptime`;
my @fields = split( /,/, $uptime );
my $load   = $fields[ -2 ];
my $colour = undef();
 
if   ( $load < 1 ) { $colour = "white"  }
elsif( $load < 2 ) { $colour = "yellow" }
elsif( $load < 3 ) { $colour = "orange" }
else               { $colour = "red"    }
 
print( STDOUT <<TXT );
<p>Load average is <font color="$colour"> $load </font></p>
<hr>
TXT
 
END

Possible (this is dynamic after all) result in the HTML:

<html>
 <head><title>SSI Test</title>
  <meta http-equiv="Refresh" content="2; test.shtml">
 </head>
 <body>
  <p>This is a big page about our large machine. </p>
  <p>Load average is <font color="white"> 0.32 </font></p>
  <hr>
 </body>
</html>

Executing arbitrary shell commands

The #exec command can also be used to execute arbitrary shell commands when used with the cmd = tag. For this tag to be available, the server needs to have `CGI enable anywhere' turned on.

<!--#exec cmd="command" -->

The server will execute the equivalent of /bin/sh -c "command" and replace the tag with the output of that command.

For example:

<!--#exec cmd="cat /etc/passwd | cut -f1 -d':' | sort" -->
Content Manager [Administrator] 16 December 2005 Bookmark with del.icio.us Post this article to Digg Post this article to reddit Post this article to Facebook Tweet this article  

Recently...

Other Resources