perl and CGI

V

Vit

Hi All,

I'm new to the perl language....

I'm trying to understand how this language work and I hav develop the
following code:

in the webpage:
<form action="\cgi-bin\my_email.cgi" method="post"> 
<input type="submit" name="Submit" value="Submit" style="width:
93px" />

in the cgi-bin directori the "my_email.cgi" file:
#!/usr/bin/perl
print "Content-type: text/html\n\n";
print "Hello, world!\n";

I'm using this file just to test.... and the result is that is not
working....

when I click to the "submit" button, I get the following message:

Server error!
The server encountered an internal error and was unable to complete
your request.

Error message:
Premature end of script headers: my_email.cgi

If you think this is a server error, please contact the webmaster.

Error 500
Tue Jun 9 14:11:00 2009
Apache/2.0.55 (Ubuntu) mod_ldap_userdir/1.1.11 PHP/4.4.2-1.1
mod_vhost_ldap/1.0.0

what can I do?? do you know what can I cahe to find out the issue???

thanks

Vit
 
J

Jürgen Exner

Vit said:
I'm new to the perl language....

Purists will likely point out that "perl" (lower case) is the
interpreter, while "Perl" (upper case) is the name of the programming
language that is interpreted by perl.
I'm trying to understand how this language work and I hav develop the
following code:

If you want to learn programming in Perl then I _STRONGLY_ suggest to
start with good old plain Perl programs and not to add the complexity
and problems of CGI, web servers, and the WWW on top of learning the
language.
in the webpage:
<form action="\cgi-bin\my_email.cgi" method="post"> 
<input type="submit" name="Submit" value="Submit" style="width:
93px" />

in the cgi-bin directori the "my_email.cgi" file:
#!/usr/bin/perl
print "Content-type: text/html\n\n";
print "Hello, world!\n";

I'm using this file just to test.... and the result is that is not
working....

when I click to the "submit" button, I get the following message:

Server error!
The server encountered an internal error and was unable to complete
your request.

Error message:
Premature end of script headers: my_email.cgi

And this is a perfect example of why mixing everything together is a bad
idea. This error message is _not_ a Perl error message.
Your program is perfectly fine. When run from the command line it will
print those intended 3 lines and then terminate without any error
message.
That means your problem lies in a different area, in your case probably
in a misunderstanding of the CGI protocol.
If you think this is a server error, please contact the webmaster.

Error 500

what can I do?? do you know what can I cahe to find out the issue???

This infamous error message is listed in the Perl FAQ, see
perldoc -q 500
for details.

jue
 
V

Vit

And this is a perfect example of why mixing everything together is a bad
idea. This error message is _not_ a Perl error message.
Your program is perfectly fine. When run from the command line it will
print those intended 3 lines and then terminate without any error
message.
That means your problem lies in a different area, in your case probably
in a misunderstanding of the CGI protocol.

thank's for the suggestion....

I was just trying to figure out how perl and the web server works..

I have already developed a perl file to manage a web form (send the
forms field to an email address)...

and the file seems to be ok..

but when I run it on the server it gives me the same error...

so I was wondering what was wrong and how can I debug the issue....

any suggestion to find out the problem??

thanks

Vit
 
J

Jürgen Exner

Vit said:
I was just trying to figure out how perl and the web server works..
I have already developed a perl file to manage a web form (send the
forms field to an email address)... and the file seems to be ok..

but when I run it on the server it gives me the same error...
so I was wondering what was wrong and how can I debug the issue....

any suggestion to find out the problem??

As I mentioned before, you DO NOT have an issue with Perl. Had you
written your program in C or Pascal or Basic or Fortran you would still
get the same error message.
Your issue is with the Common Gateway Interface. Therefore asking in a
NG that deals with CGI will probably address your problem more
accurately. Did you read the FAQ I pointed out? It contains several
pointers to more information.

jue
 
G

Gunnar Hjalmarsson

Vit said:
thank's for the suggestion....

I was just trying to figure out how perl and the web server works..

I have already developed a perl file to manage a web form (send the
forms field to an email address)...

and the file seems to be ok..

but when I run it on the server it gives me the same error...

so I was wondering what was wrong and how can I debug the issue....

any suggestion to find out the problem??

Jürgen gave you a suggestion. If you run

perldoc -q 500

at the command line, you get an entry in the Perl FAQ that mentions
various possible reasons for the error message. The document can also be
found on the web:

http://perldoc.perl.org/perlfaq9.html

Since the program looks good, let me still give you a few hints:

- Is the path to perl correct?
- Did you upload the program in ASCII / TEXT mode?
- Is the program executable? (0755 works for most web servers)
 
G

Gunnar Hjalmarsson

Jürgen Exner said:
As I mentioned before, you DO NOT have an issue with Perl. Had you
written your program in C or Pascal or Basic or Fortran you would still
get the same error message.
Your issue is with the Common Gateway Interface. Therefore asking in a
NG that deals with CGI will probably address your problem more
accurately.

Any suggestions of such a NG?
 
A

A. Sinan Unur

in the webpage:
<form action="\cgi-bin\my_email.cgi" method="post"> 

<form action="/cgi-bin/my_email.cgi" method="post">

....
in the cgi-bin directori the "my_email.cgi" file:
#!/usr/bin/perl
print "Content-type: text/html\n\n";
print "Hello, world!\n";

The content you send and the content type you specify conflict:

#!/usr/bin/perl

use strict;
use warnings;

$| = 1;

use CGI qw( -no_xhtml );

my $cgi = CGI->new;

print $cgi->header('text/html'),
$cgi->start_html(),
$cgi->p('Hello World!'),
$cgi->end_html();

__END__

Error message:
Premature end of script headers: my_email.cgi

If you think this is a server error, please contact the webmaster.

Error 500

As was pointed out, perldoc -q 500

Sinan

--
A. Sinan Unur <[email protected]>
(remove .invalid and reverse each component for email address)

comp.lang.perl.misc guidelines on the WWW:
http://www.rehabitation.com/clpmisc/
 
C

ccc31807

Hi All,

I'm new to the perl language....

I'm trying to understand how this language work and I hav develop the
following code:

Follow these three steps and this will provide a foundation:
1. Study (and I do mean STUDY) Learning Perl by Randal Schwartz
2. Study CGI/Perl by Diane Zak
3. Study the CGI documentation at the Apache Foundation website
(apache.org) with particular reference to httpd.conf (assuming that
you are using httpd to serve your your CGI scripts)

(optional) 4. I have found MySQL and Perl for the Web by Paul Dubois
valuable for actually building useful applications, and I strongly
recommend that you consider studying that book. It's not an entry
level book and you need to have a firm grasp of steps 1 through 3
before you can understand it.

CC.
 
J

Jürgen Exner

A. Sinan Unur said:
The content you send and the content type you specify conflict:

Sorry for asking stupid and even off-topic, but: while true that
shouldn't cause a server error, should it?

jue
 
J

Jürgen Exner

Gunnar Hjalmarsson said:
Any suggestions of such a NG?

I don't do CGI and am not interested in it, therefore I have no
information about the validity of any of the following NGs, which a
quick search for CGI in the NG directory of my provider returned:

comp.infosystems.www.authoring.cgi
perl.beginners.cgi

In other languages:
de.comm.infosystems.www.authoring.cgi
de.comp.lang.perl.cgi
it.comp.www.cgi
as well as several subgroups fido7.ru.cgi.* including fido7.ru.cgi.perl
in Russian

jue
 
J

J. Gleixner

Vit said:
Hi All,

I'm new to the perl language....

I'm trying to understand how this language work and I hav develop the
following code:

in the webpage:
<form action="\cgi-bin\my_email.cgi" method="post">

Change that to "/cgi-bin/my_email.cgi". Also, check in your
Web server's error log.
 
N

Nathan Keel

Jürgen Exner said:
I don't do CGI and am not interested in it, therefore I have no
information about the validity of any of the following NGs, which a
quick search for CGI in the NG directory of my provider returned:

comp.infosystems.www.authoring.cgi
perl.beginners.cgi

In other languages:
de.comm.infosystems.www.authoring.cgi
de.comp.lang.perl.cgi
it.comp.www.cgi
as well as several subgroups fido7.ru.cgi.* including
fido7.ru.cgi.perl in Russian

jue

All of the CGI groups are dead (and I mean literally dead, not just low
activity). They used to be pretty busy, but died off about 5 years
ago. There's not a lot to get Perl working for CGI, mainly just the
header output, permissions set properly and a few other minor things,
so I'm not surprised CGI specific groups are no more.
 
G

Gunnar Hjalmarsson

Jürgen Exner said:
I don't do CGI and am not interested in it,

That's what I suspected. The natural follow-up question is: Why on earth
are you so quick to reply to CGI related questions??
therefore I have no
information about the validity of any of the following NGs, which a
quick search for CGI in the NG directory of my provider returned:

comp.infosystems.www.authoring.cgi

Dead since long.
perl.beginners.cgi

NNTP interface at nntp.perl.org to the mailing list beginners-cgi
http://lists.cpan.org/showlist.cgi?name=beginners-cgi
(which actually is alive)
 
P

Peter J. Holzer

Follow these three steps and this will provide a foundation:
1. Study (and I do mean STUDY) Learning Perl by Randal Schwartz
2. Study CGI/Perl by Diane Zak
3. Study the CGI documentation at the Apache Foundation website
(apache.org) with particular reference to httpd.conf (assuming that
you are using httpd to serve your your CGI scripts)

3.5. Find out where your web server keeps the log files (especially the
error log) and READ THEM!
(optional) 4. I have found MySQL and Perl for the Web by Paul Dubois

hp
 
M

Mart van de Wege

JXrgen Exner said:
Sorry for asking stupid and even off-topic, but: while true that
shouldn't cause a server error, should it?
Indeed not. The server does not do HTML validation, that's the work of
the HTML parser on the client.

Possible causes for the error seen by the OP:

- Permissions on the CGI script are wrong.

- Webserver is looking in another directory for CGI scripts.

- I saw the OP using backslashes to specify the path in the URL. I don't
know if that's going to work with Apache (the server output mentions
it's Ubuntu, so I assume Apache as httpd).

- Perl is not in /usr/bin on the webserver.

Mart
 
G

Guy

Hi All,

I'm new to the perl language....

I'm trying to understand how this language work and I hav develop the
following code:

in the webpage:
<form action="\cgi-bin\my_email.cgi" method="post">
<input type="submit" name="Submit" value="Submit" style="width:
93px" />

in the cgi-bin directori the "my_email.cgi" file:
#!/usr/bin/perl
print "Content-type: text/html\n\n";
print "Hello, world!\n";

I'm using this file just to test.... and the result is that is not
working....

when I click to the "submit" button, I get the following message:

Server error!
The server encountered an internal error and was unable to complete
your request.

Error message:
Premature end of script headers: my_email.cgi

If you think this is a server error, please contact the webmaster.

Error 500
Tue Jun 9 14:11:00 2009
Apache/2.0.55 (Ubuntu) mod_ldap_userdir/1.1.11 PHP/4.4.2-1.1
mod_vhost_ldap/1.0.0

what can I do?? do you know what can I cahe to find out the issue???

thanks

Vit

-----------------------------
Did you solve your problem?

1. Make sure you upload your Perl script to the correct folder on your web
server, which I think would be something like /cgi-bin. Otherwise you may
get a 404 error, saying it can't find the file.

2. Once on the server, ensure that you change the file's properties to
executable, otherwise, I think you'll get error 403, something about
refusing to display web page.

3. I get the 500 Internal Server Error when I have an error in my code. The
following script for example works fine:
#!/usr/bin/perl
$command= $];
$title = "Perl Version";
print "Content-type: text/html\n\n";
print "<html><head><title>$title</title></head><body>";
print "<h1>$title</h1>\n";
print "Perl version : ".$command;
print "<HR> \n";
system 'perl -v';

It displays the following -- yes I know it would be great if I had Perl 10
:(

Perl Version
Perl version : 5.006001
-----------------------
This is perl, v5.6.1 built for i686-linux Copyright 1987-2001, Larry Wall
Perl may be copied only under the terms of either the Artistic License or
the GNU General Public License, which may be found in the Perl 5 source kit.
Complete documentation for Perl, including FAQ lists, should be found on
this system using `man perl' or `perldoc perl'. If you have access to the
Internet, point your browser at http://www.perl.com/, the Perl Home Page.

If however, I forget a semi colon like:
#!/usr/bin/perl
$command= $] # <--- Forgot Semicolon
$title = "Perl Version";
print "Content-type: text/html\n\n";
print "<html><head><title>$title</title></head><body>";
print "<h1>$title</h1>\n";
print "Perl version : ".$command;
print "<HR> \n";
system 'perl -v';

I get the following:
500 Internal Server Error
The server encountered an internal error or misconfiguration and was unable
to complete your request.
Please contact the server administrator, or webmaster and inform them of the
time the error occurred, and anything you might have done that may have
caused the error.
More information about this error may be available in the server error log.

4. You can also access your perl scripts directly instead of submitting a
form, for example, type the following in your address bar, and also use
/cgi-bin/my_email.cgi instead of \cgi-bin\my_email.cgi like Sinan said.
http://yourserver/cgi-bin/my_email.cgi

5. On a side note, I use the .pl extension instead of .cgi, but I may be a
minority? I think I even read that it was better to not use any extension
claiming that people don't have to know that the script is Perl or whatever?

6. Your print code looks ok, so perhaps the trouble is in your (pound bang)
line? Like you, mine is:
#!/usr/bin/perl
But perhaps you require it like this: (user) instead of (usr)???
#!/user/bin/perl

7. Are you sure your system supports Perl? If so, check if there are some
default Perl scripts in the /cgi-bin folder and check if they work, and if
they do, start with them.

Finally, I'm quite new to this group and Perl so I expect to be corrected
here!

PS. I recently learned that instead of uploading my scripts to test them, I
could install Strawberry Perl on my Windows XP and test my scripts locally.
I upload them to the server only once the bugs are out.

Cheers,
Guy D.
 
T

Tad J McClellan

Guy said:
Hi All,

I'm new to the perl language....


[ snip quoted text with no quote marks ]



[ snip original text, but how can anybody tell that it is not quoted? ]


Please learn the proper way of composing a followup.
 
V

Vit

Hi All,

I'm new to the perl language....

I'm trying to understand how this language work and I hav develop the
following code:

in the webpage:
<form action="\cgi-bin\my_email.cgi" method="post">
<input type="submit" name="Submit"  value="Submit" style="width:
93px" />

in the cgi-bin directori the "my_email.cgi" file:
#!/usr/bin/perl
print "Content-type: text/html\n\n";
print "Hello, world!\n";

I'm using this file just to test.... and the result is that is not
working....

when I click to the "submit" button, I get the following message:

Server error!
The server encountered an internal error and was unable to complete
your request.

Error message:
Premature end of script headers: my_email.cgi

If you think this is a server error, please contact the webmaster.

Error 500
Tue Jun 9 14:11:00 2009
Apache/2.0.55 (Ubuntu) mod_ldap_userdir/1.1.11 PHP/4.4.2-1.1
mod_vhost_ldap/1.0.0

what can I do?? do you know what can I cahe to find out the issue???

thanks

Vit

-----------------------------
Did you solve your problem?

1. Make sure you upload your Perl script to the correct folder on your web
server, which I think would be something like /cgi-bin. Otherwise you may
get a 404 error, saying it can't find the file.

2. Once on the server, ensure that you change the file's properties to
executable, otherwise, I think you'll get error 403, something about
refusing to display web page.

3. I get the 500 Internal Server Error when I have an error in my code. The
following script for example works fine:
    #!/usr/bin/perl
    $command= $];
    $title = "Perl Version";
    print "Content-type: text/html\n\n";
    print "<html><head><title>$title</title></head><body>";
    print "<h1>$title</h1>\n";
    print "Perl version : ".$command;
    print "<HR> \n";
    system 'perl -v';

It displays the following -- yes I know it would be great if I had Perl 10
:(

Perl Version
Perl version : 5.006001
-----------------------
This is perl, v5.6.1 built for i686-linux Copyright 1987-2001, Larry Wall
Perl may be copied only under the terms of either the Artistic License or
the GNU General Public License, which may be found in the Perl 5 source kit.
Complete documentation for Perl, including FAQ lists, should be found on
this system using `man perl' or `perldoc perl'. If you have access to the
Internet, point your browser athttp://www.perl.com/, the Perl Home Page.

If however, I forget a semi colon like:
    #!/usr/bin/perl
    $command= $] # <--- Forgot Semicolon
    $title = "Perl Version";
    print "Content-type: text/html\n\n";
    print "<html><head><title>$title</title></head><body>";
    print "<h1>$title</h1>\n";
    print "Perl version : ".$command;
    print "<HR> \n";
    system 'perl -v';

I get the following:
500 Internal Server Error
The server encountered an internal error or misconfiguration and was unable
to complete your request.
Please contact the server administrator, or webmaster and inform them of the
time the error occurred, and anything you might have done that may have
caused the error.
More information about this error may be available in the server error log.

4. You can also access your perl scripts directly instead of submitting a
form, for example, type the following in your address bar, and also use
/cgi-bin/my_email.cgi instead of \cgi-bin\my_email.cgi like Sinan said.
   http://yourserver/cgi-bin/my_email.cgi

5. On a side note, I use the .pl extension instead of .cgi, but I may be a
minority? I think I even read that it was better to not use any extension
claiming that people don't have to know that the script is Perl or whatever?

6. Your print code looks ok, so perhaps the trouble is in your (pound bang)
line? Like you, mine is:
    #!/usr/bin/perl
But perhaps you require it like this: (user) instead of (usr)???
    #!/user/bin/perl

7. Are you sure your system supports Perl? If so, check if there are some
default Perl scripts in the /cgi-bin folder and check if they work, and if
they do, start with them.

Finally, I'm quite new to this group and Perl so I expect to be corrected
here!

PS. I recently learned that instead of uploading my scripts to test them,I
could install Strawberry Perl on my Windows XP and test my scripts locally.
I upload them to the server only once the bugs are out.

Cheers,
Guy D.

Thanks for the answer!!! really appreciate!!!

I have solve the issue!!! was the permission on the .pl file (I set
utp the permission on the falder, but not on the file...

now I'm trying to debug my file.... it works (no error in the
browser!!!), but it is not doing what I'd like to...

#!/usr/bin/perl

&send_email;

sub send_email
{
$to = "vit\@domain.com";
open(MAIL, "|/usr/sbin/sendmail");

print MAIL "From: bob\@domain.com\n";
print MAIL "To: $to\n";
print MAIL "Subject: Web Enqiry\n\n";

close (MAIL);
}

print "Content-type: text/html\n\n";
print "Hello World2"

it doesn't give me an error, but I dont receive any mail....

any suggestion???

thanks

Vit
 
R

RedGrittyBrick

Vit said:
Hi All,

I'm new to the perl language....

I'm trying to understand how this language work and I hav develop the
following code:

in the webpage:
<form action="\cgi-bin\my_email.cgi" method="post">
<input type="submit" name="Submit" value="Submit" style="width:
93px" />

in the cgi-bin directori the "my_email.cgi" file:
#!/usr/bin/perl
print "Content-type: text/html\n\n";
print "Hello, world!\n";

I'm using this file just to test.... and the result is that is not
working....

when I click to the "submit" button, I get the following message:

Server error!
The server encountered an internal error and was unable to complete
your request.

Error message:
Premature end of script headers: my_email.cgi

If you think this is a server error, please contact the webmaster.

Error 500
Tue Jun 9 14:11:00 2009
Apache/2.0.55 (Ubuntu) mod_ldap_userdir/1.1.11 PHP/4.4.2-1.1
mod_vhost_ldap/1.0.0

what can I do?? do you know what can I cahe to find out the issue???

thanks

Vit

-----------------------------
Did you solve your problem?

1. Make sure you upload your Perl script to the correct folder on your web
server, which I think would be something like /cgi-bin. Otherwise you may
get a 404 error, saying it can't find the file.

2. Once on the server, ensure that you change the file's properties to
executable, otherwise, I think you'll get error 403, something about
refusing to display web page.

3. I get the 500 Internal Server Error when I have an error in my code. The
following script for example works fine:
#!/usr/bin/perl
$command= $];
$title = "Perl Version";
print "Content-type: text/html\n\n";
print "<html><head><title>$title</title></head><body>";
print "<h1>$title</h1>\n";
print "Perl version : ".$command;
print "<HR> \n";
system 'perl -v';

It displays the following -- yes I know it would be great if I had Perl 10
:(

Perl Version
Perl version : 5.006001
-----------------------
This is perl, v5.6.1 built for i686-linux Copyright 1987-2001, Larry Wall
Perl may be copied only under the terms of either the Artistic License or
the GNU General Public License, which may be found in the Perl 5 source kit.
Complete documentation for Perl, including FAQ lists, should be found on
this system using `man perl' or `perldoc perl'. If you have access to the
Internet, point your browser athttp://www.perl.com/, the Perl Home Page.

If however, I forget a semi colon like:
#!/usr/bin/perl
$command= $] # <--- Forgot Semicolon
$title = "Perl Version";
print "Content-type: text/html\n\n";
print "<html><head><title>$title</title></head><body>";
print "<h1>$title</h1>\n";
print "Perl version : ".$command;
print "<HR> \n";
system 'perl -v';

I get the following:
500 Internal Server Error
The server encountered an internal error or misconfiguration and was unable
to complete your request.
Please contact the server administrator, or webmaster and inform them of the
time the error occurred, and anything you might have done that may have
caused the error.
More information about this error may be available in the server error log.

4. You can also access your perl scripts directly instead of submitting a
form, for example, type the following in your address bar, and also use
/cgi-bin/my_email.cgi instead of \cgi-bin\my_email.cgi like Sinan said.
http://yourserver/cgi-bin/my_email.cgi

5. On a side note, I use the .pl extension instead of .cgi, but I may be a
minority? I think I even read that it was better to not use any extension
claiming that people don't have to know that the script is Perl or whatever?

6. Your print code looks ok, so perhaps the trouble is in your (pound bang)
line? Like you, mine is:
#!/usr/bin/perl
But perhaps you require it like this: (user) instead of (usr)???
#!/user/bin/perl

7. Are you sure your system supports Perl? If so, check if there are some
default Perl scripts in the /cgi-bin folder and check if they work, and if
they do, start with them.

Finally, I'm quite new to this group and Perl so I expect to be corrected
here!

PS. I recently learned that instead of uploading my scripts to test them, I
could install Strawberry Perl on my Windows XP and test my scripts locally.
I upload them to the server only once the bugs are out.

Cheers,
Guy D.

Thanks for the answer!!! really appreciate!!!

I have solve the issue!!! was the permission on the .pl file (I set
utp the permission on the falder, but not on the file...

now I'm trying to debug my file.... it works (no error in the
browser!!!), but it is not doing what I'd like to...

#!/usr/bin/perl

use strict;
use warnings;
use CGI;
use CGI::Carp qw(fatalsToBrowser);


&send_email;
send_email();


sub send_email
{
$to = "vit\@domain.com";
open(MAIL, "|/usr/sbin/sendmail");

Always check for success/failure when opening a file handle.
Use lexical file-handles and the three-argument open.
(assuming your ancient perl supports them)
print MAIL "From: bob\@domain.com\n";
print MAIL "To: $to\n";
print MAIL "Subject: Web Enqiry\n\n";

Aren't you supposed to provide a message body terminated by a full-stop
on a line by itself?
close (MAIL);

I imagine sendmail was waiting for a message body?
}

print "Content-type: text/html\n\n";

Don't promise HTML if you are not willing to keep your promise.
print "Hello World2"

That isn't HTML.
it doesn't give me an error,

Ask perl to tell you of any errors! (see comment above).
Make sure errors are written somewhere you are looking.
See above `use CGI::Carp qw(fatalsToBrowser);`
Back in the days of Perl 4 I used
BEGIN {
open(STDERR ,'>&STDOUT')
|| die "Can't redir stderr to out: $!\n";
$| = 1; # Make it unbuffered
print "Content-type: text/html\n\n";
}
This is more in keeping with your rather quaint and archaic coding style
but I can't imagine your Perl installation could be so backward as to
lack a better way to redirect errors to the browser.
but I dont receive any mail....

Ask Perl to tell you why.
any suggestion???

See above.

I'd make more use of modules for CGI and for email.
 

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