Where to place your
Although there is nothing dangerous about placing
cgi scripts in random directories throughout your
site, it's best if you keep them in their own little
home known as the cgi-bin. This minimizes security
risks and allows you to maintain your cgi programs
from one directory.
The path to Perl:
One of the first things you must do when configuring
a script, is set the correct path to the Perl
interpreter, which is the engine responsible for
processing the script. The path to Perl on our
servers is: #!/usr/bin/perl
The path to Sendmail:
Some programs such as the ones, which send email
will need to know where the Sendmail program resides
on the server. The script will typically have a
setting like this: $mailprog = '/usr/sbin/sendmail';
and will want you to set it appropriately. Sendmail
on our servers can be found here: /usr/sbin/sendmail or
within your cgi scripts:
When you configure a cgi script for "any" server, it
may ask you to set variables such as the base,
relative, and CGI directory/url settings. Here's an
"example" using Matt Wright's wwwboard.pl script.
Obviously, each script may vary, but this should
provide you with some basic idea:
$basedir = "/home/yourlogin/public_html/wwwboard";
$baseurl = "http://www.yoursite.com/wwwboard";
$cgi_url = "http://www.yoursite.com/cgi-bin/wwwboard.pl";
Most scripts come with documentation on how to set
these directories. Please make sure you read and
understand it before configuring the script. New to
cgi? Here is a page with questions and answers to
numerous questions evolving around the ins and outs
of using cgi within your scripts:
Another excellent site, which provides step by step
There are a number of file permissions, which can be
used for a variety of different purposes, however
we'll limit this tutorial to the ones most commonly
used. To begin with, it's important you understand
the three categories of permissions, which are:
The owner is you. In most cases, this is not so much
of a concern, as you can only obtain owner
permissions in one of two ways. 1. FTP into your
account using your Username and Password. 2. Login
via Telnet with the same information.
The represents a group of users who have access to a
particular directory. For example, a password
protected directory, whereas only members can access
it upon providing the correct Username and Password.
In this case, any permissions you assign to "Group"
would be applicable to users with access to that
This is the most important one of all. Public
permissions determine what your world wide visitors
can and cannot do with your files. ALWAYS make sure
you understand what a particular permission does
before assigning it to a file. If not, you may
wakeup to find your website demolished by some clown
who was snooping about and gained access to your
To set file permissions:
1. Login with your FTP
Open the directory where the file you wish to set
permissions on resides
Right click on the file and select CHMOD
A box similar to the one above will appear
Observe how you can
"select" the individual permissions you want, or
simply enter the 3 digit number if you know what it
is. Most instructions included with downloaded
scripts will tell or indicate this to you.
By default, all files
uploaded to the server automatically have
permissions set to 644. The setting 644 is
relatively safe, as it provides "Read" and "Write"
access to the owner, while limiting the rest of the
public to "Read Only" access.
When setting permissions for cgi scripts, the most
common permissions setting is 755. 755 allows the
owner "Read and Write" access, while allowing the
Group and Public "Read and Execute" permissions. So
what are we actually saying? In short, when users
access your cgi script, the server has been
instructed to grant them permissions to "Read and
Execute" it. Sound scary? It's not actually…
Remember that a script is a program that must be
processed by the server. As long as the script is
written properly, you can safely allow users to
execute it, and thus providing the desired results.
For example, if they wanted to post a message to
your wwwboard discussion forum, then they would need
these permissions to execute wwwboard.pl, which
would write their new message to an html file, which
is displayed on the main forum. The new message
would reside in a directory on your site so other
users could view it. Most cgi, perl and other
scripts you'll be installing come complete with
instructions telling you which permissions you'll
need to set them to.
Setting permissions on files is a relatively simple
task, however MAKE SURE you fully understand what it
is you're allowing the public to do with your files.
For example, some less experienced users often make
the fatal mistake of simply setting ALL of their
files to 777. While 777 will automatically allow
executing privileges, it also allows full "READ,
WRITE, and EXECUTION ability to the entire world!!!!
This is how web sites get hacked! While most
visitors have good intentions, all it takes is one
person whom snoops about your files seeking an "Open
Back Door." This could result is them gaining full
access to your directories, which means they can do
anything from deleting your entire site, to defacing
it with obscenities.
New to cgi? Here is a page with questions and
answers to numerous questions evolving around the
ins and outs of using cgi within your scripts:
Using Server Side
Includes - SSI
SSI works in conjunction with a web page usually
with the .shtml extension. The .shtml extension
tells the server to do something different with the
web page. When you append the .html or .htm
extension, this tells the server to "read" the page
only. The .shtml extension tells the server to
"Execute" the page, in addition to just reading it.
So, why would you want to execute the page? There
are various commands you can program into a web
page, which the server will look for and parse when
the file is called as .shtml. In many cases, this
mode is used in conjunction with Server Side Include
(SSI) tags, to call a CGI script. For example, you
have a visitor counter script, and we'll call it
count.cgi. Every time someone visits your website,
you want the script to be called, so that it logs
the visitor into a file.
To do this, you would place an SSI tag into your web
page. The tag in this case, would look something
This small tag, which is hidden in the html coding
of your page is telling the server to:
1. Go to the cgi-bin
2. Execute count.cgi
That's it! The information has been captured and
processed by the count.cgi script. Of course, that's
the short version of what happens. The long version
would no doubt, would take us far beyond the scope
of this document.
PLEASE do not use the .shtml extension on "all" of
your web pages unless it's absolutely necessary.
With a busy web site, this means that every page
must be executed, as opposed to just read. This as
you can appreciate, can add considerable memory and
CPU load to the system. As always, read the
instructions that came with your script carefully.
They should provide specific instructions on how to
configure the script, as well as the SSI tag.
The ins and outs of DNS and how it effects your