On Thu, Jan 08, 2009 at 06:47:05PM -0800, John W. Krahn wrote:
> root wrote:
> > The following script gives me confusing results.
> >I've not delved into OOP before and am surprised when something
> >appears to work but gives wrong answers.
<snip>
> >
> >foreach( @ARGV)
> >{ $target = $_;
>
> More proper as:
>
> foreach my $target ( @ARGV )
>
You're absolutely right. My excuse (you knew I'd have one) is that
this was cut from a much larger application (dir compare) where $target
needed broader scope.
> > if( $useOO)
> > { open(FILE, $target) or die "Can't open '$target': $!";
> > binmode(FILE);
>
> With modern versions of Perl you can use lexically scoped filehandles
> and the three argument form of open() which can include binmode in the mode:
>
> { open(my $FILE, '<:raw', $target) or die "Can't open '$target':
> $!";
>
I knew about the three argument form of open() but somehow missed ':raw'.
Thanks for pointing it out.
<snip>
> > local $/; # slurp mode
> >
> > return '0' if( ! -e $file);
> > open INFILE, "<$file" || die "Unable to open $file: $! stopped ";
>
> You have a precedence problem as the high precedence of the '||'
> operator means that this will not die() even if open() fails. You need
> to either use parentheses for open's arguments or use the low precedence
> 'or' operator.
I've had that (|| vs or) in my notes (Camel p.191) for three or four weeks
now but hadn't run across it when I first wrote the script.
> Also, I wouldn't use a file test operator because the result from open()
> will already tell you whether the file exists or not.
>
If I recall, the test is in there as protection against running md5sum
against a broken link. That part didn't make it into the part you saw.
Oops, my bad.
>
> > binmode(INFILE);
> > my $data = <INFILE> ;
> > close INFILE;
> > if ( $myDebug ) # this gives wrong answers
> > { $digest = Digest::MD5->md5_hex($data); }
> > else
> > { $digest = md5_hex($data); }
> > $digest;
> >}
> >__END__
>
>
> John
> --
> Those people who think they know everything are a great
> annoyance to those of us who do. -- Isaac Asimov
One of my favorite authors.
Thanks for the critique,
Mike
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