Introduction to CGI
stands for "Common Gateway Interface," a fancy name meaning computer
programs running on the web server that can be invoked from a www page
at the browser. The "bin" part alludes to the binary executables that
result from compiled or assembled programs. It is a bit misleading
because cgi's can also be Unix shell scripts or interpreted languages
like Perl. CGI scripts need to be saved in ASCII format and uploaded to
your server's cgi-bin in ASCII or text format. This is very important.
Where to Put CGI Scripts
Put your cgi-bin scripts in the www subdirectory named "cgi-bin".
Paths to Date, Mail, Perl, etc.
Here are your paths to the common server resources that CGI scripts often require:
Root path: /home/username/ (puts you in your the root of your account)
Domain directory: /home/username/domainname-www (puts you in your www directory)
Cgi-bin path: /home/username/domainname-www/cgi-bin/filename (puts you in your cgi-bin)
NOTE: Do not include domain extension anywhere you list your domain name.
Permissions - Definitions and Overview
order for your CGI program to run, it must be executable by the server.
Therefore, you must set the permissions so the server can read or
execute your files, which usually means making your CGI programs world
executable. The way you set your file permissions is by using the CHMOD
CHMODï¿½s permission mask is a three-digit number. Each digit of the
number defines the permission for a different user of the file. The
first digit defines the permission for the owner, the second digit
defines the permissions for the group and the third digit defines the
permissions for everyone else (referred to by CuteFTP as public). Each
digit works the same for each group of users: the owner, group, and
public. What you set for one digit has no effect on the other two
Owner = the files users (you)
Group = the files group
Others = others
r = read access
x = execute access
w = write access
r = 4
x = 2
w = 1
will come to recognize, if you do not already, Chmod as a word used for
changing Permissions from within Telnet or your FTP client.
Some scripts will tell you to chmod 775 (for example). When using the numeric system, the code for permissions is as follows:
4 + 2 + 1 (rwx) = 7
first number applies to Owner, the second number applies to Group, and
the third number applies to Others. Therefore the first 7 of the chmod
775 tells Unix to change the Owner's permissions to rxw (because r=4 +
w=2 + x=1 adds up to 7, this giving the Owner Read, Write, and Execute
Permission. The second 7 applies to the group, this giving the Group
Read, Write, and Execute Permission, and the last number 5, refers to
Others (4 + 1= 5), giving Others only Read and Execute Permission. The
permissions for chmod 775 look like this: rwx rwx -rx.
are always broken up into three groups of letters, however if there is a
dash, this dash simply means that Permission wasn't given for that
particular function, for example in the chmod 775, Permission to Write
was not given to Others.
Remember: the first 3 letters always apply to Owner, the second 3 apply to Group, and the third 3 apply to Others.
How do I set permissions for my cgi scripts?
There are three different ways to set permissions for your files and directories within your account.
- File Manager
We DO NOT encourage the use of Telnet if it is only being used for
setting permissions and will forego its explanation here.
Setting Permissions Using Your File Manager:
into your Control Panel and then click on File Manager. You will now
see a list of directories within the root of your account. Since all of
your html files and subdirectories are uploaded and created within your
www directory you need to click on the directory labeled "www".
inside your www folder, you will see, as in all directories, the first
column is the Permissions Column, click on the link pertaining to the
directory or file that you wish to set the settings for and the
Permissions screen. (Refer to Permission Definitions further down this
page for an explanation of settings.)
Setting Permissions using Fetch for MAC:
you have Fetch for the Mac, you have an easy way to change permissions.
Go to the file you want to change the permissions on, and highlight it.
Under the Remote menu, select Change Permissions. A window will pop up
showing the current permissions for the file you had highlighted. Click
on the boxes to change permissions as needed. (Refer to the Permission
Definitions further down this page for an explanation of settings.
Setting Permissions Using WS_FTP for Windows:
accomplishes the same task as above. Just highlight the file you want
to check, and right-click on it. A menu will pop up, then select CHMOD. A
window will pop up, click on the appropriate settings as needed. (Refer
to the Permission Definitions further down this page for an explanation
Setting Permissions Using CUTE FTP:
the Menu Bar, click Commands/File Actions/CHMOD to change the
attributes of a file or folder on the server. In the Change Attributes
dialog box, select the Read, Write, or Execute options for each group
(Owner, Group and Public) or type in the corresponding CHMOD command in
the manual box.
Troubleshooting CGI-bin Problems
Below are solutions to some of the more common CGI script problems.
I activate my CGI program, I get back a page that says "Internal Server
Error. The server encountered an internal error or mis-configuration
and was unable to complete your request."
is generally caused by a problem within the script. Check your script
settings again to see that you have entered the correct server
information and have set the correct permissions for the script. If this
information is correct, you'll need to contact whoever wrote or is
distributing the script for further assistance.
I am being told "File Not Found," or "No Such File or Directory."
Upload your Perl or CGI scripts in ASCII mode, not binary mode.
I test my Perl script in local mode (by Telnet), I have the following
error: "Literal @domain now requires a back slash at myscript.pl line 3,
within string. Execution of myscript.pl aborted due to compilation
This is caused by a misinterpretation
by Perl. You see, the "@" sign has a special meaning in Perl; it
identifies an array (a table of elements). Since it cannot find the
array named domain, it generates an error. You should place a back slash
(\) before the "@" symbol to tell Perl to see it as a regular symbol,
as in an email address.
I am getting the message "POST not implemented."
are probably using the wrong reference for cgiemail. Use the reference
/cgi-bin/cgiemail/mail.txt. Another possibility is that you are pointing
to a cgi-bin script that you have not put in your cgi-bin directory. In
general, this message really means that the web server is not
recognizing the cgi-bin script you are calling as a program. It thinks
it is a regular text file.