Why does my Perl CGI program return a server error?

问题

I recently got into learning cgi and I set up an Ubuntu server in vbox. The first program I wrote was in Python using vim through ssh. Then I installed Eclipse on my Windows 7 station and created the exact same Perl file; just a simple hello world deal.

I tried running it, and I was getting a 500 on it, while the Python code in the same dir (/usr/lib/cgi-bin) was showing up fine. Frustrated, I checked and triple-checked the permissions and that it began with #!/usr/bin/perl. I also checked whether or not AddHandler was set to .pl. Everything was set fine, and on a whim I decided to write the same exact code within the server using vim like I did with the Python file.

Lo and behold, it worked. I compared them, thinking I'd gone mad, and they are exactly the same. So, what's the deal? Why is a file made in Windows 7 on Eclipse different than a file made in Ubuntu server with vim? Do they have different binary headers or something? This can really affect my development environment.

#!/usr/bin/perl
print "Content-type: text/html\n\n";
print "Testing.";

Apache error log:

[Tue Aug 07 12:32:02 2012] [error] [client 192.168.1.8] (2)No such file or directory:     exec of '/usr/lib/cgi-bin/test.pl' failed
[Tue Aug 07 12:32:02 2012] [error] [client 192.168.1.8] Premature end of script headers: test.pl
[Tue Aug 07 12:32:02 2012] [error] [client 192.168.1.8] File does not exist: /var/www/favicon.ico

This is the continuing error I get.

回答1:

I think you have some spurious \r characters on the first line of your Perl script when you write it in Windows.

For example I created the following file on Windows:

#!/usr/bin/perl

code goes here

When viewed with hexdump it shows:

00000000  23 21 2f 75 73 72 2f 62  69 6e 2f 70 65 72 6c 0d  |#!/usr/bin/perl.|
00000010  0a 0d 0a 63 6f 64 65 20  67 6f 65 73 20 68 65 72  |...code goes her|
00000020  65 0d 0a                                          |e..|
00000023

Notice the 0d - \r that I've marked out in that. If I try and run this using ./test.pl I get:

zsh: ./test.pl: bad interpreter: /usr/bin/perl^M: no such file or directory

Whereas if I write the same code in Vim on a UNIX machine I get:

00000000  23 21 2f 75 73 72 2f 62  69 6e 2f 70 65 72 6c 0a  |#!/usr/bin/perl.|
00000010  0a 63 6f 64 65 20 67 6f  65 73 20 68 65 72 65 0a  |.code goes here.|
00000020

You can fix this in one of several ways:

You can probably make your editor save "UNIX line endings" or similar.
You can run dos2unix or similar on the file after saving it
You can use sed: sed -e 's/\r//g' or similar.

Your apache logs should be able to confirm this (If they don't crank up the logging a bit on your development server).

回答2:

Sure, it can.

One environment might have a module installed that the other might not.
Perl might be installed in different locations in the two environment.
The environments might have different versions of Perl.
The environments might have different operating systems.
The permissions might be setup incorrectly in one of the environments.
etc

But instead of speculating wildly like this, why don't you check the error log for what error you actually got?

回答3:

No, they are just text files. Of course, it's possible to write unportable programs, trivially by using system() or other similar services which depend on the environment.

来源：https://stackoverflow.com/questions/11850192/why-does-my-perl-cgi-program-return-a-server-error

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