Installing Your Own CGIs
You can install your own custom developed CGI scripts or CGI scripts that you have downloaded from
a third party source (see CGI
Security Issues).
This document is divided into several sections. Each section includes a discussion about a specific
topic. Each topic, though important, may or may not have applicability to your specific situation.
The "Virtual Environment"
Your Basic Web Hosting account services operate in an environment completely separate
of the root system (and any other Basic Plus account hosted on the same host machine). This means that
your script does not have access to any files residing on the root file system, only those files that
are located in your home directory hierarchy.
Path Specification
Because your CGI scripts operate in a "Virtual Environment" (see above), the pathnames that
you specify in your CGI scripts should be declared with respect to your home directory. For example,
your script may access a file to read from or write to. Specify a pathname that begins with
/home/LOGIN/www/cgi-bin/
Setting Permissions
After you have uploaded your script or have created it on-line, make sure you give the script permission
to execute. In a UNIX environment, each file has a specific mode or set of permissions which determine
who can read or write to the file as well as who can execute the file (if anyone). Setting the
"execute bit" on a file is easy to do. You can either use
iManager or most FTP clients:
% chmod +x FILENAME
where FILENAME is the name of your script. If a script does not have execute permissions, your
web server will report a "403 Forbidden" server error when it attempts to
execute the script.
Common Problems with Perl Scripts
- Failure to upload your Perl script in ASCII mode.
Perl scripts, unlike compiled executables, are plain text files. Plain text files should be
transferred from your local computer to your Virtual Server using ASCII mode (not BINARY mode).
Failure to transfer your Perl scripts to your Virtual Server in ASCII mode may result in 500
Server Errors.
- Improper path specification of Perl interpreter.
The first line of a Perl script indicates the path name of the Perl interpreter. In the FreeBSD
Basic Plus environment, the correct specification of your Perl 4 interpreter is /usr/local/bin/perl.
If you downloaded a Perl script from a third party source, the Perl interpreter is most often
defined based on the author's host environment which may be different from the Virtual Server
environment (/usr/bin/perl is a fairly common however).
Troubleshooting 500 Server Errors
If you encounter the enigmatic "500 Server Error" when you execute your scripts, the best way
to diagnose the actual source of the problem is to examine your web server's error log. Your error log
is typically stored in your ~/www/logs directory under the name error_log.
To review the server error generated in real time, perform the following steps:
- Review the error_log file at:
http://your-domain.com/logs/error_log
- Using your browser, attempt to execute your CGI script again. When
you do this, the actual error message will be displayed in your Telnet
session.
Some commonly encountered errors with their corresponding solutions are given below.
| Error: |
| HTTPd/CGI: exec of [CGI PATH INFO] failed, errno is 2 |
| Analysis and Solution: |
| The first line of your CGI script failed to specify the correct location of
the interpreter. If your script is written in Perl, please see the "Common Problems with Perl
Scripts" section above for the proper first line definition of the Perl interpreter. If your
Perl interpreter definition is correct, it is very likely that you uploaded the script in BINARY
mode from your Windows machine to your Virtual Server. If you originally uploaded the script in
BINARY mode, re-upload the script in ASCII mode to correct the problem.
|
| |
| Error: |
| HTTPd: malformed header from script [CGI PATH INFO] |
| Analysis and Solution: |
Your script is not printing out a proper header response. When a CGI is
executed, it communicates back to the web server a message which is divided into two parts: the
header and the body. The header typically tells the web server the "content type" of the
data that will be sent as the body of the response. The header and body are separated by a single
blank line. An example of a CGI response is shown below:
Content-type: text/html
<html>
<head><title>Title</title></head>
<body bgcolor="white">
Hello world!
</body>
</html>
The "malformed header from script" error message indicates that your script is not
properly returning the header portion of the response. You may not have misspelled
"Content-type", not supplied a valid type (such as "text/html"), or failed to
print out a blank line to separate the header from body of the response.
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