Simple Perl / CGI script to calculate BMI

The Common Gateway Interface example from a Well House Consultants training course
More on The Common Gateway Interface [link]

This example is described in the following article(s):
• Teaching examples in Perl - third and final part - [link]

Source code: slip Module: P403

#!/usr/bin/env perl

# ($height, $weight) = ($ENV{QUERY_STRING} =~ /h=(.*)&w=(.*)/ );
# Previous line worked for specific form / numeric inputs

# Handle inputs via the default GET method

@parts = split(/\&/,$ENV{QUERY_STRING});
        foreach $p (@parts) {
                ($n,$v) = split(/=/,$p);
                $v =~ tr/+/ /;
                $v =~ s/%(..)/pack("C",hex($1))/eg;
                $tabl{$n} = $v;
        }

# Subroutine to clean up inputs so they can be echoed

sub webify {
        $_ = $_[0];
        s/&/&/g;
        s/</</g;
        return $_;
        }

$height = $tabl{h};
$weight = $tabl{w};

$ech_h = webify($height);
$ech_w = webify($weight);

# represents the work ...
# -----------------------

$status = `uptime`;
$discs = `df -k`;
if ($height > 0) {
        $bmi = $weight / ($height * $height);
} else {
        $bmi = '[result space]';
        }

# Send output - MANDATORY Header, MANDATORY blank line, content

print "Content-type: text/html\n\n";
print <<"STUFF"
<html>
<head><title>BMI demo</title></head>
<body><h1>Perl Course Demo</h1>
Input height = $ech_h and weight = $ech_w<br><br>
About the system ... $status<br><br>
Disc usage ... <br>
<pre>$discs</pre><br><br>
The BMI is $bmi<br><br>
<form>
Height <input name=h><br>
Weight <input name=w><br>
<input type=submit></form>
<hr>
Copyright ....
</body></html>
STUFF
;

__END__

Sample output:

<html>
<head><title>BMI demo</title></head>
<body><h1>Perl Course Demo</h1>
Input height = 1.77 and weight = 65<br><br>
About the system ... 13:41:30 up 66 days, 7:23, 0 users, load average: 0.09, 0.21, 0.27
<br><br>
Disc usage ... <br>
<pre>Filesystem 1K-blocks Used Available Use% Mounted on
/dev/sda3 73520780 47961544 21764284 69% /
/dev/sda1 194442 11683 172720 7% /boot
tmpfs 452264 0 452264 0% /dev/shm
</pre><br><br>
The BMI is 20.7475501931118<br><br>
<form>
Height <input name=h><br>

Weight <input name=w><br>
<input type=submit></form>
<hr>
Copyright ....
</body></html>

Learn about this subject

This module and example are covered on the following public courses:
* Deploying LAMP - Linux, Apache, MySQL, Perl/PHP
* Linux Web Server
* Using Perl on the Web
Also available on on site courses for larger groups

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