Understanding CGI Basics

Understanding the Basic of CGI

Q. What Is CGI and how is it going to help me?
A. CGI is translated as Common Gateway Interface.  It's used to provide interactivity and turn static pages into dynamic ones.  What does this mean?  Let's take a guestbook, for example.  Most of them are powered by CGI.  They allow your visitors to leave comments on your site.  This makes it interactive.  But guestbooks are only one example.  You also have bulletin boards, form processing, counters, and much more.

Q. How am I supposed to install a script?
A. 95% of scripts have complete instructions and a special ReadMe file with everything you need to know about installing that script.  It is recommended that you read the instructions a few times before starting to install the script.  This will help you make less mistakes.

Q. What does "chmod" mean?
A. To chmod a file means to set a certain permission.  Few of the most common chmod commands are 775 and 777.  To chmod a certain file or a category using FTP client find something like "Change File Attributes" and enter the chmod command script instructions tell you.  If you are using SSH, here are a few options that you should use in order to chmod a file or a directory:

u = the file's user (or owner)
r = read access
g = the file's group
x = execute access
o = others
w = write access
a = the user, the group, and others.

Q. What are the most common errors and how do I deal with them?
A. One of the most common errors is "500 Internal Error".  The chances are that you will experience it many times.  The worst thing about it is that it doesn't actually tell you what's wrong with the script.  It only tells you that something isn't right. There are several possibilities that make up 99% of this error.  They are:

* Incorrect path to PERL. See the next question for more information
* Syntax error. Check and see if you didn't accidentally deleted a command or a word that the instructions didn't tell you to.
* Incorrect CHMOD command. Make sure that you chmod the file exactly as the instructions say. Most of the times it will be either 755 or 777 (not always!). You can also get an "Access Denied" error, if you didn't chmod the file or a directory correctly.

Basically, 500 Internal Error and Access Denied are 99% of errors you'll experience.  And 99% of the time, the cause of the error will be one of the above.

Q. What is the path to PERL (interpreter)?
A. The PERL path is the very first line in every .cgi or .pl file.  Usually it looks something like this: #!/usr/bin/perl.  Make sure that the path is correct, otherwise you'll get an error.  If you don't have SSH access, simply contact support.
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