Contentsggnindia.dronacharya.info/IT/Downloads/SubInfo/6thSem/PPT/Web... · PERL Syntax Overview...
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Contents • Introduction • A simple Program in PERL • PERL Syntax • PERL File Extension • Variable types • First CGI Program • Complete CGI program using PERL • Applications • Scope of Research
Transcript of Contentsggnindia.dronacharya.info/IT/Downloads/SubInfo/6thSem/PPT/Web... · PERL Syntax Overview...
Contents
• Introduction
• A simple Program in PERL
• PERL Syntax
• PERL File Extension
• Variable types
• First CGI Program
• Complete CGI program using PERL
• Applications
• Scope of Research
Introduction
Since we have covered In this lecture we will be studying
basics of PERL programming and how to write a
complete CGI program using PERL
A simple “Hello World” Program in PERL
#!/usr/local/bin/perl
print "Hello World";
The #!/usr/local/bin/perl line. Put this in the top of the file.
Line No 1. What does it do? This tells the system where the
perl interpreter is located. Different systems may have perl at
different locations. Sometimes it will be #!/usr/bin/perl.
Now if you are using perl in Windows, the script will run
without this line..
PERL Syntax Overview
• There is no need to have a main() function or anything of that kind.
• Perl statements end in a semi-colon:
print "Hello, world";
• Comments start with a hash symbol and run to the end of the line:
# This is a comment
• Whitespace is irrelevant:
print "Hello, world";
• ... except inside quoted strings:
# this would print with a line break in the middle
print "Hello world";
• Double quotes or single quotes may be used around literal strings:
print "Hello, world";
print 'Hello, world';
• However, only double quotes "interpolate" variables and special characters such as newlines (\n ):
print "Hello, $name\n"; # works fine
print 'Hello, $name\n'; # prints $name\n literally
• Numbers don't need quotes around them:
print 42;
• You can use parentheses for functions' arguments or omit them according to your personal taste. Following two statements produce same result.
print("Hello, world\n");
print "Hello, world\n";
PERL File Extension
Regardless of the program you choose to use, a PERL
file must be saved with a .pl (.PL) file extension in order
to be recognized as a functioning PERL script.
So, Type this above in a text editor like notepad and
save this to a file called 'hello.pl'. If you are using
Linux/Unix, run the command 'perl hello.pl'. If you are
using Windows and you have installed ActivePerl, just
double click the file and the script will be executed by
the interpreter.
variable types
Perl has three built in variable types:
Scalar
Array
Hash
Scalar variable type
A scalar represents a single value as follows:
my $animal = "camel"; my $answer = 42;
Scalar values can be used in various ways:
print $animal;
print "The animal is $animal\n";
print "The square of $answer is ", $answer * $answer,
"\n";
Array variable type
• An array represents a list of values:
my @animals = ("camel", "llama", "owl");
my @numbers = (23, 42, 69);
my @mixed = ("camel", 42, 1.23);
• Arrays are zero-indexed but you can change this setting by changing default variable $[ or $ARRAY_BASE. Here's how you get at elements in an array:
print $animals[0]; # prints "camel“
print $animals[1]; # prints "llama"
Hash variable type
• A hash represents a set of key/value pairs. They are prefixed by % sign as follows:
my %fruit_color = ("apple", "red", "banana", "yellow");
• You can use whitespace and the => operator to lay them out more nicely:
my %fruit_color = ( apple => "red", banana => "yellow",);
• To get a hash elements:
$fruit_color{"apple"}; # gives "red“
• You can get at lists of keys and values with keys() and values() built-in functions.
my @fruits = keys %fruit_colors;
my @colors = values %fruit_colors;
First CGI Program
#!/usr/bin/perl
print "Content-type:text/html\r\n\r\n";
print '<html>';
print '<head>';
print '<title>Hello Word - First CGI Program</title>';
print '</head>';
print '<body>';
print '<h2>Hello Word! This is my first CGI program</h2>';
print '</body>';
print '</html>';
If you click hello.cgi then this produces following output:
Hello Word! This is my first CGI program
Lets make a little form. Save the following into a file called
guestbook.htm
<html>
<head><title>Guestbook</title></head>
<body>
<form action="/cgi-bin/guestbook.pl" method="get">
<table>
<tr><td>Name</td>
<td><input name="name" type="text" value=""></td></tr>
<tr><td>E-Mail</td>
<td><input name="email" type="text" value=""></td></tr>
<tr><td>Location</td><td>
<input name="loc" type="text" value=""></td></tr>
<tr><td>Comments</td>
<td><TEXTAREA name="comments" rows="10" cols="32“></TEXTAREA></td></tr>
</table>
<br><br><input type="submit" value="Add Entry"></form>
</body></html>
result
Now lets create a perl script to get the input from this file.
Create a file called 'guestbook.pl' in the cgi-bin folder
#!/usr/local/bin/perl
#Now lets get the input
my $query_string = "";
#Get the input
if ($ENV{REQUEST_METHOD} eq 'POST') {read(STDIN, $query_string, $ENV{CONTENT_LENGTH});
}
else {$query_string = $ENV{QUERY_STRING};
}
##### We will remove this
print "Content-Type: text/html\n\n";
print "Query String is \n<br> $query_string";
• Now put the perl file(save the above lines to a file called guestbook.pl) in the cgi-bin folder. Now copy the guestbook.htm file to the documents folder - the root folder. Now fire up your server and open the guestbook.htm file from within the server
• you will see the html file we created here. Now enter the below given values
Name - Binny E-Mail - [email protected] Location - Omnipresent Comments - Hello World! Here I am. and press the "Add Entry" button.
• Now you will be taken to another page. If there is some mistake, it will be an error page. If not, the address bar will look something like this...
http://127.0.0.1/cgi-bin/guestbook.pl?name=Binny&[email protected]&loc=Omnipresent&comments=Hello+World%21+Here+I+am.
• This is the information that was passed between two files. Now the content part will look like this.
• Query String is name=Binny&[email protected]&loc=Omnipresent&comments=Hello+World%21+Here+I+am.
• This is the data we got from the form.
The full script will look something like this...
#!/usr/local/bin/perl
my $query_string = '';
#Get the input
if ($ENV{REQUEST_METHOD} eq 'POST')
{read(STDIN, $query_string, $ENV{CONTENT_LENGTH});
}
else
{$query_string = $ENV{QUERY_STRING};}
# Split the name-value pairs
@pairs = split(/&/, $query_string);
foreach $pair (@pairs)
{ ($name, $value) = split(/=/, $pair);
# Making the input English. And removing unwanted things
$value =~ tr/+/ /;
$value =~ s/%([a-fA-F0-9][a-fA-F0-9])/pack("C", hex($1))/eg;
$FORM{$name} = $value;}
#Give output
print <<START;
Content-Type: text/html\n\n
<html>
<head><title>Guest book Result</title>
<body>
<h1 align="center">Guest book Results</h1>
Dear $FORM{'name'},<BR>Thank You for filling out our Guest Book. I appreciate this effort in your part.<br><br>
<table>
<tr><td>Name</td>
<td>$FORM{'name'}</td></tr>
<tr><td>E Mail</td>
<td><a href="mailto:$FORM{'email'}">$FORM{'email'}</a></td></tr>
<tr><td>Location</td>
<td>$FORM{'loc'}</td></tr>
<tr><td>Comments</td><td>
$FORM{'comments'}</td></tr>
</table> </body>
</html>
START
# Open Guest Book
Fileopen (FILE, ">>guests.txt") || die "Can't open
guests.txt: $!\n";
#Write the information to the file
print FILE "$FORM{'name'} came from
$FORM{'loc'}.";
print FILE "E-mail address is $FORM{'email'}.";
print FILE "Comments : $FORM{'comments'}\n";
close(FILE);
Output
Completed Websites based on
CGI::Application
• These are examples of completed websites based on CGI::Application.
Source code is usually not available.
• proyectoweb2.com
– Centro de capacitacion use CMS - CGI::Application
• Unlibrary.com
– book sharing and cataloging site, uses CGI::Application, My SQL, Apache on Linux
• Dis-Order (metal music webshop)
– uses CGI::App, Postgre SQL, Apache (mod_perl) on Free BSD
• Adopt-A-Pet.com, by Summersault. Also uses mod_perl.
• Page-A-Day® Calendars Online
– CGI::Application, My SQL & Apache on Linux
• Workman.com
– Ajax, site search, shopping cart and Gift-O-Matic are all CGI::Apps
• iMeleon photography
– uses CGI::App, My SQL, Apache on Linux
• And Many more..
Scope of Research
Popularity Contest for CPAN Modules
Offline Command Line Search for CPAN
Which tests matter?
Binary CPAN mirror
Assignment 14
What is difference between CGI and Perl?
