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How to debug the CGI program
- Thread starter rubis
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Well, a very basic thing to do is to comment chunks of the code, and start uncommenting block by block, until you find all possible bugs.
It's also very usesful to look at the error log of your webserver, as all messages are logged there. If you have an apache webserver, it's probably at
/var/log/httpd/error_log
Wiz
It's also very usesful to look at the error log of your webserver, as all messages are logged there. If you have an apache webserver, it's probably at
/var/log/httpd/error_log
Wiz
a few strategies.....
1 - make sure your syntax works from a command prompt
That will check your syntax without running the code.
2 - Instead of using the 'die' function, use a small
sub routine to report errors. Like,
open(FILE,"<Some_file"
or oooops("Failed to open Some_file, $!"
while(<FILE>)....
close FILE;
sub oooops
{
my $error = shift;
print "<p>$error</p></body></html>";
exit;
}
Use something like this everywhere you MIGHT have a significant failure (eg. opening a file).
3 - You can run your CGI from a command prompt. Obviously,
if the output is really large then this becomes a little
tedious, but, it will allow you to see the output of your
code.
'hope this helps
If you are new to Tek-Tips, please use descriptive titles, check the FAQs, and beware the evil typo.
1 - make sure your syntax works from a command prompt
Code:
C:\perl -c your_code.cgi =return=That will check your syntax without running the code.
2 - Instead of using the 'die' function, use a small
sub routine to report errors. Like,
open(FILE,"<Some_file"
or oooops("Failed to open Some_file, $!"while(<FILE>)....
close FILE;
sub oooops
{
my $error = shift;
print "<p>$error</p></body></html>";
exit;
}
Use something like this everywhere you MIGHT have a significant failure (eg. opening a file).
3 - You can run your CGI from a command prompt. Obviously,
if the output is really large then this becomes a little
tedious, but, it will allow you to see the output of your
code.
'hope this helps
If you are new to Tek-Tips, please use descriptive titles, check the FAQs, and beware the evil typo.
If you must run in a browser this line will help on Apache servers
#######REMOVE LATER
use CGI::Carp qw(fatalsToBrowser);
This dumps errors out to the browser instead of the serverlog. It may help.. On IIS servers the browser is defaulted as the area to dump errors.
SERVER 500 ERROR!
There are several reasons for it but the most common one is a script inabilty to find a file that is requested by 'use' or 'require' statements. Check these statments to make sure all the paths are correct.
Beware the dreded typo in the path.
I agree with goboatings ideas, make sure the syntax is ok first.
#######REMOVE LATER
use CGI::Carp qw(fatalsToBrowser);
This dumps errors out to the browser instead of the serverlog. It may help.. On IIS servers the browser is defaulted as the area to dump errors.
SERVER 500 ERROR!
There are several reasons for it but the most common one is a script inabilty to find a file that is requested by 'use' or 'require' statements. Check these statments to make sure all the paths are correct.
Beware the dreded typo in the path.
I agree with goboatings ideas, make sure the syntax is ok first.
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