Use Strict & subs

Mayhem50 has asked for the wisdom of the Perl Monks concerning the following question:

Hi Everyone, I'm fairly new to Perl through been using it for a while I never really go into the 'use Strict thing'. Now I’m writing me Perl code I want to start doing a better job of it.

Anyway when I use 'use strict' on the CGI below I get errors about the '$IMPUT' variable and that I should declare it. I’ve tried putting my in front of it when I pass the values in into it and even creating a empty version at the start of the script with ‘My $INPUT = “”;’ but I just can’t figure it out. I’m sure it’s real simple but I’ve spent a day looking for the answer with no luck. Thanks in advance guys.

#!c:/Perl/bin/Perl.exe -w
use strict;
use CGI;
print "Content-type: text/html\r\n\r\n";
# PDF 2 JPEG CGI
my $INPUT = ();
&DecodeInURL();
my $PDF2JPGEXE = 'C:\_TestSite\PDF2JPG\bin\pdf2jpeg.exe';

my $PDFFile = $INPUT{"file"};
print "**$PDFFile<br>";

my $output = 'Out_Temp\TempPDF%3.3d.jpg';
my $PDF2JPG_OutPut = system("$PDF2JPGEXE -w -d 90 -q 80 -s 240 300 -f 
+ $PDFFile $output");
print "<p>Output: $PDF2JPG_OutPut";




sub DecodeInURL {
    
    my $Decoded = $ENV{'QUERY_STRING'}; #Get Method
    $Decoded =~ s/%([\a-fA-F0-9][a-fA-F0-9])/pack('C', hex($1))/eg;
    print "$Decoded\n";
    my @INPUTVars = split /\&/ , $Decoded;
    foreach  my $pair (@INPUTVars) {
        if ($pair=~m/([^=]+)=(.*)/) {
            my $field = $1;
            my $Value = $2;
            $Value =~ s/\+/ /g;
            $INPUT{$field}=$Value;

            return $INPUT;
        }
    }
}
[download]

Comment on Use Strict & subs Download Code

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Re: Use Strict & subs by duff (Parson) on Dec 30, 2004 at 05:08 UTC
`$INPUT` is declared just fine, but `%INPUT` however is not. And `%INPUT` is the variable you're using when you say `$INPUT{$field}=$Value;` duff	[reply] [d/l] [select]
Re: Use Strict & subs by Errto (Vicar) on Dec 30, 2004 at 05:40 UTC
A more general comment: if you are going to `use CGI`, you should take advantage of the functionality that it offers you. First, you should create a CGI object by saying `my $q = CGI->new`. Then your input parsing line would look like `my $PDFFile = $q->param("file");` and you don't need any variables like $INPUT or %INPUT. You also don't need DecodeInURL - just get rid of it. Furthermore, instead of `print "Content-type: text/html\r\n\r\n";` you could simply use `print $q->header("text/html");`. Finally, though you may know this already, I should point out that the call to system does not return the output of the "pdf2jpeg" command, but rather its exit code, which is just a number. So this number is what will be displayed on the line that says "Output:" I'm not sure how exit codes work in Windows, but in Unix, and exit code of zero means success.	[reply] [d/l] [select]
Re^2: Use Strict & subs by jbrugger (Parson) on Dec 30, 2004 at 07:23 UTC
Just a little comment. i'd be careful using CGI, this module is a real good hack, but BIG (using 3,5 mb of your memory when compiled). Next, i don't really like the idea of using the html stuff CGI offers, i like my perl code to be perl, not html. You might Have a look at HTML::Template, or try the Tal implementation for perl: Petal. I don't want to create a flame about CGI versus other methods (like Apache::Request), but i'd like to inform about the possibilities, since CGI might not be the best solution for some problems. hmm updated since last comment: I'd use either the module HTML::Template or Pental (the Plone template system) to conform more to the Model-View-Controller patterns, and use templates and these modules to generate the html-content in stead of CGI Next i'd use the Apache::Request implementation to read any requests, it has the same interface as CGI, but is light and fast in use. More information can be found on http://www.cpan.org and www.plone.org.	[reply]
Re^3: Use Strict & subs by dragonchild (Archbishop) on Dec 30, 2004 at 13:41 UTC
While technically true, your comment would be better suited if you explained further why someone should use HTML::Template instead of CGI. Furthermore, what is a "Tal" implementation? For the record, I know what those things are. But, you're giving an answer to someone who doesn't seem to have a lot of domain experience in the web applications world. You need to explain what you're talking about and why someone should make a radical paradigm shift. Being right, does not endow the right to be rude; politeness costs nothing. Being unknowing, is not the same as being stupid. Expressing a contrary opinion, whether to the individual or the group, is more often a sign of deeper thought than of cantankerous belligerence. Do not mistake your goals as the only goals; your opinion as the only opinion; your confidence as correctness. Saying you know better is not the same as explaining you know better.	[reply]
Re^3: Use Strict & subs by davorg (Chancellor) on Jan 02, 2005 at 16:48 UTC
i'd be careful using CGI, this module is a real good hack, but BIG (using 3,5 mb of your memory when compiled). It's worth pointing out that whilst it's true that CGI.pm contains a lot code, it also implements a pretty ingenious code loader that it only actually compiles the code that you use. So you shouldn't really worry about loading code that you aren't going to use - CGI.pm is actually pretty efficient. -- <http://www.dave.org.uk> "The first rule of Perl club is you do not talk about Perl club." -- Chip Salzenberg	[reply]
Re: Use Strict & subs by Mayhem50 (Novice) on Dec 30, 2004 at 05:30 UTC
Thanks Duff i just added a 'My %Input =();' and away it went. I 've never delt with a hash other than set out like this '$INPUT{$field}=$Value;' and when use strict is off it works just fine. How newb was that, Thanks again!	[reply]
Re: Use Strict & subs by swaroop.m (Monk) on Dec 30, 2004 at 14:44 UTC
I guess your intention is the following. use strict; use CGI; print "Content-type: text/html\r\n\r\n"; # PDF 2 JPEG CGI my %INPUT = &DecodeInURL(); my $PDF2JPGEXE = 'C:\_TestSite\PDF2JPG\bin\pdf2jpeg.exe'; my $PDFFile = $INPUT{"file"}; print "*$PDFFile<br>"; my $output = 'Out_Temp\TempPDF%3.3d.jpg'; my $PDF2JPG_OutPut = system("$PDF2JPGEXE -w -d 90 -q 80 -s 240 300 -f + $PDFFile $output"); print "<p>Output: $PDF2JPG_OutPut"; sub DecodeInURL { my $Decoded = $ENV{'QUERY_STRING'}; #Get Method my %INPUT; $Decoded =~ s/%([\a-fA-F0-9][a-fA-F0-9])/pack('C', hex($1))/eg; print "$Decoded\n"; my @INPUTVars = split /\&/ , $Decoded; foreach my $pair (@INPUTVars) { if ($pair=~m/([^=]+)=(.)/) { my $field = $1; my $Value = $2; $Value =~ s/\+/ /g; $INPUT{$field}=$Value; return %INPUT; } } } [download]	[reply] [d/l]
Re: Use Strict & subs by sasikumar (Monk) on Dec 30, 2004 at 05:51 UTC
Hi Mayhem50 Perl treats $INPUT{$field} as a hash variable. without using stricts it works because it will lexically create a variable called %INPUT inside the sub. So it would work well without using strict. When you use strict , we need to explicitly declare the variable.So be sure what data type you would want to use. if you need a scalar $INPUT then remove `$INPUT{$field}=$Value;` as this is not the right way to store a value in scalar. Else if you want to store a vector ie hash then declare your variable as `my %INPUT=();` and also remove the `return $INPUT` statement. NOTE: FYI %INPUT and $INPUT are two different varibales and can coexist. so you can declare `my ($INPUT,%INPUT);` Thanks SasiKumar	[reply] [d/l] [select]