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Lecture Notes-PDF

Spring '01 Ad: Enrollment info

Course Info: Homework Assignments:
Practice Exams:
PIC: 
                           












HW3 Solutions Page

Return to homework page. 

#!/usr/local/bin/perl


#
# FileName: p40hw3file1.cgi
#
# Purpose: This program maintains a database of remote hosts who have
#          accessed this script and how many times they have done it.
#          It returns an HTML file displaying a table of these statistics.
#

my %table;
my $remoteHost= $ENV{REMOTE_HOST};

BeginHtml();

MakeHead("Remote Host Counter");

BeginBody();

%table = GetUpdate("data", $remoteHost);
DrawTable($remoteHost, %table);

EndBody();
EndHtml();

#
# Function: GetUpdate($dataFile, $remHost)
#
# Purpose: reads in table of (remotehost count) pairs from the file $datafile
#          add one to the count of $remHost and write back out the result
#
# Remarks: In the specification of the homework GetUpdate didn't
#          have a second argument. However, it seemed cleaner this way.
#          If you did it either way in your solution you will receive full
#          credit.
#

sub GetUpdate
{
	my $dataFile = $_[0];
	my $remHost = $_[1];
	my %hostTable;
	my $host;
	my $cnt;

	#Read in file

	open(IN, $dataFile);
	while(<IN>)
	{
		chomp;
		($host, $cnt) = split;
		$hostTable{$host} = $cnt;
	}
	close(IN);

	#Check if $remHost row exists if not create

	if(!$hostTable{$remHost})
		{$hostTable{$remHost}=0;
		}


	$hostTable{$remHost}++; # bump count of this site

	#Write out file

	open(OUT, ">$dataFile");

	foreach $key (keys (%hostTable))
	{
		print OUT "$key $hostTable{$key}\n";
	}
	close(OUT);

	return %hostTable;
}

#
# Function: DrawTable($host, %table)
#
# Purpose: outputs the html for a table that lists the
#          number of times each address has accessed
#          the given machine. This information if passed
#          into the function via %table.
#

sub DrawTable
{
	my $host;
	my %table;
	($host, %table) = @_;


print <<THEADSTART;

<table width="100%" border="2" cellpadding="4" >
<tr>
<td bgcolor="gray" color="black">

<h1><b>Welcome.</b> You are the <tt style="background: black;
color:white">
THEADSTART

printf("%04d</tt> visitor from <tt>$host.</tt></h1>\n", $table{$host});

print <<THEADFINISH;

<p>Below is a frequency table of other sites requesting this page:
</p>
</td>
</tr>

<tr bgcolor="gray" color="black">
<td>
<table width = "100%" border="0" cellpadding ="0">
<tr>
THEADFINISH

	foreach $key (keys (%table)) #print out rows of the table
	{
	  if($key eq $host) {next;}

	  print "<tr><td><tt>$key</tt></td>\n";
	  print "<td><tt style=\"background: black; color: white\">";
	  printf("%04d</tt></td></tr>\n",$table{$key});
	}

print <<TFINISH;

</table>

</td>
</tr>
</table>
TFINISH

} #END of DrawTable functions

#
# Function: MakeHead($title)
#
# Purpose: given a $title passed as it 0th argument, this
#          function output the head part of an html
#          document with that $title.
#

sub MakeHead
{
	my $title=$_[0];
	print "<head><title>$title</title></head>\n"
}

#
# Function: BeginHtml
#
# Purpose: Outputs the content-type and
#          begin document tag for an Html document
#

sub BeginHtml
{
	print "Content-type: text/html\n\n";
	print "<html>\n";
}

#
# Function: EndHtml
#
# Purpose: Outputs the end document tag for an Html document
#

sub EndHtml
{
	print "</html>\n";
}

#
# Function: BeginBody
#
# Purpose: Outputs the start body tag for an Html document
#

sub BeginBody
{
	print "<body>\n";
}

#
# Function: EndBody
#
# Purpose: Outputs the end body tag for an Html document
#

sub EndBody
{
	print "</body>\n";
}