CGI Script Installation Tutorial 10.Learn from the Errors!
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Benny Alexander
December 23, 2004
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Mostly, we can
figure out the mistakes from the type of error which the browser shows.
Hopefully there is no bug in the script itself. (Let us believe the script is
well written and has been checked in various environments). Here are some
possible major error messages which may occur:
1.
Server: Error 500 or Internal server error:
You can get a server error
500 for many reasons, some of which occur IF
the script does not contain the
"#!/usr/local/bin/perl" header line that points to the Perl interpreter, or if
the path to the interpreter (and/or a library file) is invalid. the
first line output from the script is not a valid HTTP header (i.e.
"Content-type: text/html"), or there is NO blank line after the header
data. there
is a syntax error in your script. Always run it from the command-line first.
Check
to make sure that the ACTION="" of your script is pointing to the correct CGI
program. If it is, make sure that this file is also chmoded 755 so that
everyone, including the Web Server User ID has permission to execute it.
Make
sure all files to be opened during execution by the script are chmoded so that
the web server can read them Check
all paths to certain commands and make sure they are correct. An incorrect path
in your script will cause execution of your script to halt
Check
them and run the script again. I hope you've got it!
2.
Error 403 "File Not Found"
Make sure that all of the URLs are correct in
the scripts and that when the necessary portions of certain URLs are combined
they form complete URL. Many do enter the URLs wrong or do not change them from
the standard distribution. You can avoid this by double checking your
entries.
3.
Error 501 "Cannot POST to non-script area..."
CGI scripts can be
configured to run on most systems in two ways, the first, inside a cgi-bin
directory. Error 501 usually says that the server does not support the method
POST to a non script area. This means that since you do not have your files in a
server defined cgi-bin, the server will not allow the POST method to these
files, and will not execute these scripts.
Simply linking from your page to
an executable program or script won't cause it to be run on the server. There
are two common arrangements: either files in directories especially designated
by the server administrator are executed as CGI scripts, or files with a special
extension (such as .cgi) are executed as CGI scripts. Some times you may need to
rename PL files into .cgi to make the server understand your script type, but
this is very rare.
These are just two possible ways your server might be
configured. Many sites don't allow users to run CGI scripts at all. Consult your
web server's administrator and make sure that you have the access for a
cgi-bin..
4.
"File Does Not Exist"
This error is generally caused by the wrong path.
Make sure that the path is to Perl. (Like " /usr/bin/perl") Also make sure that
the path in your HTML document is correct.
5. When One
Browser Works and Another Doesn't
Some browsers are tolerant of
incorrect Content-type headers, as well as of null characters in text/html or
text/plain output. Make sure your output is strictly correct; it helps to check
the script with different browsers.
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