Perl 101: The email form - Hello world in Perl (
Page 2 of 5 )
As is tradition, we'll start with a Hello
World example in Perl:
#!/usr/bin/perl
print
"Content-type:text/html\n\n";
print "Hello World"; Type this
script into your favourite text editor (notepad, wordpad, pico etc) and save it
as hello.pl. Next, upload it to the cgi directory of your webserver - typically
this will be called 'cgi' or 'cgi-bin' and will be located inside your main web
directory.
The next step is one that often trips up newbies, so make
sure you are happy with what is happening. On Unix systems, files have
permissions that govern who are allowed to access them. Typically you would set
the permissions on your files so that anybody can view them but only you (the
administrator) can write/delete them. In the case of CGI scripts, you need to
make your scripts executable by anyone.
With a text based FTP client you
would do so with the following command:
chmod 755
hello.pl If you are using a graphical client such as CuteFTP,
right clicking on a file should give you the option to change its permissions.
Fire up your web browser and navigate to
http://www.yoursite.com/cgi-bin/hello.pl. If all goes well you should see 'Hello
World' at the top of your screen. Unfortunately, this being your first CGI
script, things might not go so smoothly. The most common problem is a "500
Internal Server Error" message. This usually indicates a typo in your script, so
go back and check it. In particular, make sure that each line ends with a ; and
that the very first line is #!/usr/bin/perl. Occasionally Perl will be installed
in a different location to this - check your web hosts help pages or contact
their support department if you are unsure.
If you browser simply
displays the source code of your script, this indicates that the web server did
not recognise the file as a program to run. The most common cause of this is
incorrect file permissions - go back and make sure that your script is world
executable (755 or rwxr-xr-x).
Anyway, hopefully this has wetted your
appetite for PERL CGI. Through the remainder of this article, I will take you on
a step by step journey through the process of creating a simple 'mail me'
script.
Getting Data Into The Script CGI's real power comes
from its ability to read user input, process it, then spit out a response; but
first we need a way to get user information into the script. HTML forms are the
most common way to do this, so we'll spend a moment or two going over them.
A form consists of a combination of check-boxes, radio buttons, text
boxes etc, as well as a field telling the browser where to send the data to once
the form has been submitted. A typical form may look something like this:
<form
action="http://www.myurl.com/cgi-bin/info.pl" method=post>
Enter Your
Name: <input type=text name=mytext><br><br>
<input
type="submit">
</form> This would display a
rectangular box for users to enter their name, and a grey 'submit' button. Note
the <form action="http://www.myurl.com/cgi-bin/info.pl" method=post> tag.
This instructs the browser to navigate to the info.pl script when you click on
the submit button.
In our example we need fields for Name, Email Address
and Message, so our form would be:
<form
action="http://www.yoururl/cgi-bin/mailme.pl" method=post>
Your Name :
<input type=text name=name><br>
Email Address : <input
type=text name=email><br><br>
Your Message :<br>
<textarea name=message cols=40
rows=10></textarea><br><br>
<input type=submit
value="send message">
</form> Copy this into your
text editor and save it as mailme.html. Upload it to your web server as you
would any other HTML file. Make sure you change the forms action attribute so
that it points to your web site. Don't worry that the mailme.pl script doesn't
exist yet - we'll be creating that in the next section.
Browse to the
mailme.html page with your web browser, and you should see something like this:
You can also of course paste this code into an existing
html page to integrate it better into your site.{mospagebreak title=Parsing User
Input&toc=1} Now that we have the form setup, we need a way to get the user
supplied data into our script. For the sake of simplicity we’re going to use the
CGI module that makes retrieving user input a piece of cake.
#!/usr/bin/perl First off we tell Perl to use the
CGI module:
use CGI; The CGI module
an object orientated module, so we create a reference ($q) to a new instance of
it:
$q = new CGI; We can now
retrieve the data stored in each element of the form by passing the elements
name to our CGI object:
$name =
$q->param("name");
$email = $q->param("email");
$message =
$q->param("message"); If you look back to our HTML form
code on the previous page, then you will see that 'name', 'email', and 'message'
match up with the name=values in the code.
It really is that easy with
CGI. Don't worry if this talk of modules and object orientated programming is
confusing you: for now just realize that we can retrieve form data using
$variable = $q->("element name"), where "element name" is the name you gave
to the field in your HTML form.
Just to prove that the script is
working, we'll finish off with the following lines:
print "Content-type:text/html\n\n";
print
"<html><body>";
print "Name $name<br>";
print "Email
Address $email<br>";
print "Message : $message<br>";
...which will display the data read in by the script.
Our script
so far then looks like this:
#!/usr/bin/perl
use CGI;
$q = new CGI;
$name = $q->param("name");
$email = $q->param("email");
$message = $q->param("message");
print "Content-type:text/html\n\n";
print
"<html><body>";
print "Name $name<br>";
print "Email
Address $email<br>";
print "Message : $message<br>";
Save this script as mailme.pl and upload it to your CGI-BIN directory
(remembering to CHMOD 755 it). Go back to the HTML form in your web browser,
fill in some value and click submit. If all goes well, you will see the values
displayed back to you.
Sending the email Next comes the code
to actually send the email. Typically Perl scripters use the Unix program
"sendmail". Sendmail is present on almost all Unix/Linux systems, is highly
configurable, and runs via the command line - all this makes it the ideal choice
for sending email through perl.
First off you need to know the location
of sendmail on your webserver, however. Again, consult your web hosts help pages
or contact them if you are unsure. Most often it resides in the
/usr/lib/sendmail directory:
$sendmailpath =
"/usr/lib/sendmail"; Next, we open a pipe to sendmail. Pipes are
an advanced feature of Perl with lots of intricacies that I can't even begin to
explain here. Basically they allow us to send (i.e. pipe) data backwards and
forwards between two programs. In this case we open a pipe to sendmail and pipe
our email message to it:
open(MAIL, "|
$sendmailpath -t"); Here we've opened a pipe called "MAIL". The |
indicated that we are piping data *to* sendmail (rather than reading data *from*
sendmail), and the -t switch tells sendmail that we are specifying the recipient
of the email with a To:<email address> field.
By printing to the
pipe MAIL, we can send our data to sendmail, so we do something like this:
print MAIL "To: $myemail";
print MAIL "Reply:
$email";
print MAIL "Subject:Webmail from $name";
print MAIL "\n";
print MAIL "$message"; You'll recognise the variables $email,
$name, and $message - they are holding the data we read in from the form. The
fourth line is simply a \n (a new line break) - this is used to separate the
header of the email from the body.
$myemail should be set to hold your
email address (i.e. the address which the mail will be sent to). You can do this
by adding the following line:
$myemail =
"pete\@p-smith.co.uk"; ..towards the top of your script. Perl
treats @ as a special character, so you'll need to escape it with a forward
slash: \@
Finally, we close the pipe and send some output to the user:
close MAIL;
print "Content-type:text/html\n\n";
print "<html><body>Thank you for your comments, you mail has
been sent";
