Making Your Web Page
Interactive with CGI
TLN Technology Committee
February 16, 1999
What is CGI?
“A method used by www pages to
communicate with programs run on
the web server.”
Glossary of Internet Terms
Finding Scripts
 Matt’s Script Archive
 worldwidemart.com/scripts
 CGI Resource Index
 www.cgi-resources.com
 Web Scripts
 awsd.com/scripts/
Downloading
 Once you’ve found the script you want,
download it and all the associated
readme and html files.
 Be sure to download in ascii text mode.


If available, save individual files instead of
.zip file. This is the easiest way to ensure
that the files are saved in ascii format.
If you must use the .zip file, open files in
word after unzipping them to save them in
ascii format.
Recognizing Ascii Format
Customizing Scripts
Customizing Scripts
 The first line of the .pl script must read:
• #!/usr/bin/perl
• NOT #!/usr/local/bin/perl
 Change script name to “name.cgi”
• The .pl tag is not recognized on the server.
• Only scripts with the .cgi tag will run properly.
Customizing Scripts
The absolute path should be structured
as follows:
• /mnt/web/guide/worldwidemart/scripts/
• /home/lvcc/lvcc/www/cgi-bin/
 The url path to the designated file is
the full path:
• http://tln.lib.mi.us/~lvcc/cgi-bin/scriptname.cgi
• http://tln.lib.mi.us/~lvcc/relatedwebpage.htm
Uploading Files
Creating the CGI Directory
and Uploading Files
 The CGI-BIN Directory

Working in your FTP software:
• Open your www directory
• Create a new folder at the host within the www
directory.
• Name the folder cgi-bin
 Uploading Files

Working in your FTP software:
• Upload .cgi files to cgi-bin directory
• Upload .htm files to the regular www directory
Setting Permissions
CHMOD
Changing Read/Write/Execute
Access for CGI Files
 Permission settings for each associated
file depends upon the action of the
script.
 The readme file will usually tell you
which permissions to assign to each file.
Chmod in Linux/Unix
 Www Long List of Directory
drwxr-xr-x 2 lvcc users
-rw-r--r-- 1 lvcc users
-rw-r--r-- 1 lvcc users
-rw-rw-rw- 1 lvcc users
-rw-r--r-- 1 lvcc users
1024 Jan 15 10:02 cgi-bin
1213 Jul 17 1996 momdad.htm
6520 Jul 2 1998 money.jpg
2968 Jan 7 19:15 mypet.htm
1942 Jun 22 1998 mypetadd.htm
 Cgi-bin Long List of Directory
-rw-r--r-- 1 lvcc users
-rwxr-xr-x 1 lvcc users
-rwxr-xr-x 1 lvcc users
-rwxr-xr-x 1 lvcc users
394 Aug 5 09:54 folks02.gif
24292 May 11 1998 formmail.cgi
11340 Jun 22 1998 mypet.cgi
11380 Jan 14 1998 pineknob.cgi
Changing Read/Write/Execute
Access for CGI Files
Who
u user
Opcode
+ add
g group o other
remove
= assign
Permission
r
read
w
write
x
execute
a all
chmod u=rwx,g=rx,o=rx form.cgi
CHMOD by Numbers
Readme files will
often use numbers
to designate chmod
settings.
• First digit = u
• Second digit = g
• Third digit = o
• 4 (r) + 2 (w) + 1 (x) = 7
• 4 (r) + 1 (x) = 5
chmod u=rwx,g=rx,o=rx form.cgi and
chmod 755 form.cgi result in the same action.
Running The Script
Testing and Troubleshooting
 Scripts must be uploaded and
permissions changed before they can
be tested.
 Usually, a minor adjustment will correct
script error messages.

Incorrect directory information or a
misplaced slash will prevent a script from
running.
Common Error Messages
The Form Mail Script
In Action