Beefy Boxes and Bandwidth Generously Provided by pair Networks
Do you know where your variables are?
 
PerlMonks  

Don't want to have to use -w

by Benahimvp (Initiate)
on Jul 17, 2002 at 18:13 UTC ( #182536=perlquestion: print w/ replies, xml ) Need Help??
Benahimvp has asked for the wisdom of the Perl Monks concerning the following question:

I'm a newbie to this site and I wasn't sure whether to post this in this category or debuggin. I'm running Perl 5.6 on a Linux box running Apache. So I created this test script:
#!/usr/bin/perl use CGI; require "../common.sub"; use CGI::Carp qw(fatalsToBrowser); print "Content-type: text/html\n\n"; print "Hello World";
and it wouldn't work on the web. I checked the server error logs and it said something about premature end of script. However when I ran it from the command line, it worked just fine. I searched the Perl forum cuz I knew something like this was probably common. I found out that if I put the "-w" option with the shebang line, it works fine on the web. So I have two questions. Why is that? And what do I need to do so that I don't have to use -w? You see I'm moving my site from a Win NT computer to a Linux cluster. I never had to use the -w on the Windows computer, but now I do. I thought Perl on Windows is the same as Perl on Linux. I don't want to have to go back through all my scripts and add in -w just so it would work. So how can I make it work without "-w"? I've asked this question and two other forums and people still haven't been able to figure out why this happens. Thanks for your help.

Comment on Don't want to have to use -w
Download Code
Re: Don't want to have to use -w
by DamnDirtyApe (Curate) on Jul 17, 2002 at 18:32 UTC

    From perldoc perlrun:

    -w prints warnings about dubious constructs, such as variable names that are mentioned only once and scalar variables that are used before being set, redefined subroutines, references to undefined file­ handles or filehandles opened read-only that you are attempting to write on, values used as a number that doesn't look like numbers, using an array as though it were a scalar, if your subroutines recurse more than 100 deep, and innumerable other things. This switch really just enables the internal "^$W" variable. You can disable or promote into fatal errors specific warnings using "__WARN__" hooks, as described in the perlvar manpage and the warn entry in the perlfunc manpage. See also the perldiag man­ page and the perltrap manpage. A new, fine-grained warning facility is also available if you want to manipulate entire classes of warnings; see the warn­ ings manpage or the perllexwarn manpage.

    Adding -w to your code should not affect whether or not your code runs; it should just give you a better idea why when it doesn't.

    Another option is to use the use warnings pragma in your code.

Re: Don't want to have to use -w
by DamnDirtyApe (Curate) on Jul 17, 2002 at 18:38 UTC
    I don't want to have to go back through all my scripts and add in -w just so it would work.

    It's not as hard as you might think:

    perl -p -i.bak -e 's/^(#!.*perl)/$1 -w/' *.pl
Re: Don't want to have to use -w
by gav^ (Curate) on Jul 17, 2002 at 19:47 UTC
    I think you'll find it is a problem with line endings and if you upload the script in ASCII (if you are uploading with ftp) it will work fine.

Re: Don't want to have to use -w
by BrowserUk (Pope) on Jul 17, 2002 at 20:34 UTC

    Small (potential) clarification.

    The winNT box probably had a file association (the NT ~equivalent of shebang lines) set up as:

    assoc .pl=perl_script ftype perl_script=c:\perl\bin\perl.exe -w %1 %*

    Which means that your scripts probably were being invoked with -w.

    If you choose to use DirtyDamnApe's one-liner to update your CGI script shebang lines, it would make sense (from a security point of view) to make them -Tw to enable taint checking. (See perlman:perlsec)

Re: Don't want to have to use -w
by Benahimvp (Initiate) on Jul 17, 2002 at 22:05 UTC
    Thanks guys for your help. To reply to gav^, I created the file using the vi editor, so I don't see why there should be a problem with the line endings. Also, thank you, DamnDirtyApe, for the one-liner. If I already have some files with "-w" would it affect it (make it "-w -w"), or will it just not consider it?

Log In?
Username:
Password:

What's my password?
Create A New User
Node Status?
node history
Node Type: perlquestion [id://182536]
Approved by TStanley
help
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others wandering the Monastery: (8)
As of 2014-07-31 10:20 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    My favorite superfluous repetitious redundant duplicative phrase is:









    Results (248 votes), past polls