CGI

Introduction
Common Gateway Interface. These are usually quite small ( though not always ! ) programs that can be run from the browser. Basically you upload a CGI script to the server then when someone views a page on your site it ' calls ' this script which is then run in the viewers browser. They can be used for many different purposes.

What are the ' Paths ' on my server?
Most CGI scripts require you to enter some details about the server and how it is configured, this should be all the information you need :

Perl 5 is installed and the path is : #!/usr/bin/perl
The base path to your Web directory is : /home/sites/www.yoursite.com/web
The path to sendmail program is : /usr/sbin/sendmail

What is CHMOD or setting permissions?
OK, when someone views one of your websites pages which calls a CGI script the they have to have permission to use that file.

Linux / Unix has 3 settings for the type of user and three settings for the permission of that user.

Owner This is the person that uploaded the file
Group If you have used the ' add user ' in your siteadmin then everyone her is considered part of the group.
Other Not surprisingly this means everyone else.

You can set each of these to have certain permissions for a file

Read They can read the file, IE just view it
Write They can write to the file, IE add to it or edit it.
Execute They can run the file.

To set permissions in most FTP programs you right click on the file which brings up a list of commands. Select CHMOD

I've got the idea of CHMOD but what do the numbers mean?
You will find quite often that you are told to CHMOD 755 a CGI file, this is what it means :

Each of the above permissions is given a value :

Read = 4
Write = 2
Execute = 1

In the example we have CHMOD 755

The first digit refers to the owners permission :
Read, Write and Execute = 4+2+1 = 7

The second digit is for the groups permission :
Read and Execute = 4+1 = 5

The third digit is for everyone else :
Read and Execute = 4+1 = 5

How should I upload and download CGI scripts?
Your FTP program should give you a couple of options on how to handle files. these are usually Binary or ASCII ... sometimes they throw in Automatic as well :o)

Whenever dealing with CGI scripts ALWAYS use ASCII otherwise the scripts could become corrupt and not work.

How do I edit a CGI script?
Once you have the script on your computer just open it up with a basic text editor, avoid more complicated programs like Word and just stick to something like notepad.

Should I use .pl or .cgi extensions to a CGI script?
On our servers you can use either.

Where should I put the CGI scripts?
Once you have logged into your account with FTP you will see a cgi-bin in your web directory ... all scripts should be uploaded to here.