Dr. Greg Jones - Fall 2002

CECS 5100

Survey of Educational Computer Languages

Fall 2002

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October 10th, 2002

Introduction
Audio (575k 1:13)
1. Midterm Review
2. Assignment 3a review
3. CGI (Common gateway Interface) GET and PUT
MidTerm Review
Audio (1.5M 3:29)

Relative and Absolute File References as it relates to PERL and HTML

Audio (960k 2:03)

Relative: open (GRADES, "grades") or die "Can't open grades: $!\n";
Absolute: open (GRADES, "/home/gjones/grades") or die "Can't open grades: $!\n";

Relative: <a href="index.html"></a>

Absolute: <a href="http://saturn.cecs.unt.edu/~gjones/index.html"></a>

Review Assignment 3A

Audio (224k 0:28)

Example Data referred to in the audio:

     Greg   25
     Ron    80
     Joe    40
     Greg   28

Audio (560k 1:11)	#!/usr/bin/perl
Audio (1.2M 2:47)	open (GRADES, "grades") or die "Can't open grades: $!\n";
Audio (9.8M 21:35)	while ($line = <GRADES>) { ($student, $grade) = split (" ", $line); $grades{$student} .= $grade . " "; # $grades{$student} .= $grade . " pts "; # print "'$grade','$grades{$student}'\n"; }
Audio (680k 1:26)	print "Content-type: text/html\n\n"; print "<html><body>\n"; print "<h2>Assignment #3 (part a) - Your Name</h2>\n"; print "<p>\n"; print "<table border=1>\n";
Audio (4.8M 10:35)	foreach $student (sort keys %grades) { $scores = 0; $total = 0; @grades = split (" ", $grades{$student}); foreach $grade (@grades) { $total += $grade; $scores++; } $average = $total / $scores; print "<tr><td>"; print "$student: $grades{$student}"; print "</td><td>"; print "Average: $average"; print "</td></tr>\n"; } print "</table>\n"; print "</body></html>";

Common Gateway Interface (CGI)
Audio (2.2M 4:54)

GET and POST methods of sending from a browser to a CGI

Audio (5.1M 11:16)

GET:

http://saturn.cecs.unt.edu/cgi-bin/gjones/example1.cgi?varname=value&
      varname2=value+value2&varname3=value%30

A-Z,
a-z,
0-9,
? (begins the GET),
& (delimiter of value pairs),
+ (space),
%## (extended ascii)

Example of CGI $ENV variables:

#!/usr/bin/perl

# example1.cgi

# Print out a content-type for HTTP/1.0 compatibility
print "Content-type: text/html\n\n";

print "<html><body>

About this Server<p>

<pre>
Server Name:        $ENV{SERVER_NAME}
Listening on Port:  $ENV{SERVER_PORT}
Server Software:    $ENV{SERVER_SOFTWARE}
Server Protocol:    $ENV{SERVER_PROTOCOL}
CGI Version:        $ENV{GATEWAY_INTERFACE}
</pre>

CONTENT_LENGTH = '$ENV{'CONTENT_LENGTH'}' 
QUERY STRING = $ENV{'QUERY_STRING'}


</body></html>";

POST:
form.html


<html>
<body>

<h2>Assignment 3b (Your Name Here)</h2>
<form action="http://saturn.cecs.unt.edu/cgi-bin/gjones/example1.cgi" method="POST">
    Name: <INPUT NAME="name" TYPE="TEXT" SIZE="40">
<P>
<b>Thank you!</b> <INPUT TYPE="SUBMIT" value="Submit Request"> 
</FORM>


</body>
</html>

example2.cgi: getting data sent by GET or POST

#!/usr/bin/perl

# Print out a content-type for HTTP/1.0 compatibility
print "Content-type: text/html\n\n";
print "<html><body>";

# Determine where the info is coming from
  if ($ENV{'REQUEST_METHOD'} eq "POST") {
    read(STDIN, $buffer, $ENV{'CONTENT_LENGTH'});
  } else {
    $buffer = $ENV{'QUERY_STRING'};
  }

# Split the name-value pairs
@pairs = split(/&/, $buffer);

foreach $pair (@pairs)
{
    ($name, $value) = split(/=/, $pair);

    # Un-Webify plus signs and %-encoding
    $value =~ tr/+/ /;
    $value =~ s/%([a-fA-F0-9][a-fA-F0-9])/pack("C", hex($1))/eg;
    $value =~ s/~!/ ~!/g;

    # Uncomment for debugging purposes
    print "Setting $name to $value<P>";

    $FORM{$name} = $value;
}

Example of reading then outputting form information:

#!/usr/bin/perl

# Print out a content-type for HTTP/1.0 compatibility
print "Content-type: text/html\n\n";

# Determine where the info is coming from
  if ($ENV{'REQUEST_METHOD'} eq "POST") {
    read(STDIN, $buffer, $ENV{'CONTENT_LENGTH'});
  } else {
    $buffer = $ENV{'QUERY_STRING'};
  }

# Split the name-value pairs
@pairs = split(/&/, $buffer);

foreach $pair (@pairs)
{
    ($name, $value) = split(/=/, $pair);

    # Un-Webify plus signs and %-encoding
    $value =~ tr/+/ /;
    $value =~ s/%([a-fA-F0-9][a-fA-F0-9])/pack("C", hex($1))/eg;
    $value =~ s/~!/ ~!/g;

    # Uncomment for debugging purposes
    #print "Setting $name to '$value'<P>";

    $FORM{$name} = $value;
}


print "<html><body>";
print "<h2>Example use of Hash from Form</h2>";
print "<pre>";
$fullname = join (" ",$FORM{'first'},$FORM{'MI'},$FORM{'surname'});
print "Name:         $fullname<p>";
print "</pre>";

print "
<form action=\"http://saturn.cecs.unt.edu/cgi-bin/gjones/greg.cgi\" method=\"POST\">
<P><b>Please enter your name:</b>
    First name: <INPUT NAME=\"first\" TYPE=\"TEXT\" SIZE=\"12\" MAXLENGTH=\"20\">
</form>
";

print "</body></html>";

Examples of Split and Hash:

#!/usr/bin/perl

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

# You store the string into the hash array $FORM using the index value of 'test'.
$FORM{'test'} = "Dr Greg Jones University of North Texas";

# The first split uses assigned variables to place the values from the string
($a, $b, $c, $d, $e, $f, $g) = split (" ", $FORM{'test'});

# this print statement prints out the assigned variable set above
print "'$a', '$b', '$c', '$d', '$e', '$f', '$g' <p>\n";


# Instead of assigning each variable as above,
# you use the @tests method to place them in their own HASH array
@tests = split (" ", $FORM{'test'});

# use the foreach loop to walk through each assigned values in the hash array tests
foreach $test (@tests) {
        print "'$test', ";
}

print "<p>\n";