CS 463/563 Web Programming - CGI/Perl

Perl in Internet Applications

A CGI Shell
```
#!/usr/bin/perl						#(1)
# Module which implements common CGI handling routines
require 'cgi-lib.cgi';				#(2)

# Initialization code goes here		#(3)
									#(4)
if ($ENV{'REQUEST_METHOD'} eq 'GET') {  # Send them the form
#	GET Method code goes here
} elsif ($ENV{'REQUEST_METHOD'} eq 'POST') {  # Send them the form
#	POST Method code goes here
}	#POST

# Finalization Code goes here		#(5)

# Sub-routines go here				#(6)

# End of Program
```
1. OS might require a path to the Perl interpreter
2. Any require/use statements go here (cgi-lib.cgi is on the book's CD)
3. Any common initialization code goes here.
4. The GET method is the default and is usually sent to indicate that a form is to be returned. The POST method is usually returned after the form has been filled out and data needs to be passed to the module.
5. Any common finalization code goes here.
6. Keep all subroutines at the end for ease of maintenance.

Hello World Example

#Hello World program

print <<EOF;
Content-type: text/html

<HTML>
<HEAD>
	<TITLE>Hello World!</TITLE>
</HEAD>

<BODY>
Hello World!
</BODY>
</HTML>
EOF
	;

Hello World Example (with subroutines)

#Hello World program
require 'cgi-lib.cgi';

print &PrintHeader();

$title = 'Hello World!';
print &HtmlTop();
print "Hello World!\n";
print &HtmlBot();

# PrintHeader
# Returns the magic line which tells WWW that we're an HTML document

sub PrintHeader {
  return "Content-type: text/html\n\n";
}

# HtmlTop
# Returns the head of an HTML document and the beginning of the body

sub HtmlTop {
  local ($title) = @_;

  return <<END_OF_TEXT;
  	<HTML>
	<HEAD>
	<TITLE>$title</TITLE>
	</HEAD>

	<BODY>
	<H1>$title</H1>
	END_OF_TEXT
				;
}

# HtmlBot
# Returns the bottom of an HTML document

sub HtmlBot {
  return "</BODY>\n</HTML>\n";
}

"Hello World" Interactive

#Interactive Hello World program (uses CGI handling routines)
require 'cgi-lib.cgi';

$HtmlAction = 'hello.pl';

if (&MethGet()) {		# send the form
	print &PrintHeader();
	$title = 'Hello World Interactive';
	print &HtmlTop();
	
	print <<EOT;
	<FORM ACTION="$HtmlAction" METHOD=POST>
	Please enter your first name:
	<INPUT SIZE=20 NAME="fname"><P>
	<INPUT TYPE=SUBMIT>
	<INPUT TYPE=RESET>
	</FORM>
	EOT
		;
	print &HtmlBot();
}
elsif (&MethPost()) {		# process the form
	&ReadParse();

	print &PrintHeader();
	$title = 'Hello World Interactive';
	print &HtmlTop();
	print "Hello, &in{'fname'}!";
	print &HtmlBot();
}

Hello World Hello World (Source Code)
Simple Array Example Simple Array Example (Source Code)
Test Form for parsing Source code for parseform.cgi Unparsed text

CGI Scripting with the UNIX Shell

How CGI Scipts Work, a Redux

#!/bin/sh -f
echo "Content-type: text/html"
echo ""
echo "<HTML><HEAD><TITLE>Hello World!</TITLE></HEAD><BODY>"
echo "<H1>Hello World</H1>"
echo "</BODY></HTML>"
exit 0

Local Time and Who's Logged In

#!/bin/sh -f
echo "Content-type: text/html"
echo ""
echo "<HTML><HEAD><TITLE>Local Time</TITLE></HEAD><BODY>"
echo -n "<H1>Welcome to "
hostname
echo -n "It's "
date
echo </H1>"
echo "Here's Who is Logged In Right Now:"
echo "<BLOCKQUOTE><PRE>"
who
echo "</BLOCKQUOTE></PRE>"
echo "</BODY></HTML>"
exit 0