On Jan 9, Parker, Robin said:
>foreach @array_of_files
>{
> unless (-r $_ && -w $_)
> {
> print"***Error : Cannot find file $_\n";
> }
> OPEN(FILE, $_) or die etc.......
This code doesn't work -- if you're going to write code, please make sure
you've checked it.
> while (<FILE>)
> {
> /^\b$word\b/ && $wordfound++;
> }
> close (FILE);
> unless ($wordfound)
> {
> print"*** Error : word not found in file $_\n";
> }
> $wordfound = 0;
>}
>Now I understand that this won't work 'cause while will kill off foreach's
>$_. However, I tried something with a variable called $storage.
>
>I added it in here...
>
> $storage = $_;
> while(<FILE>) {
> }
> $_ = $storage;
> close (FILE);
The more common approach would be:
for $file (@list_of_files) {
open FILE, $file;
while (<FILE>) { ... }
close FILE;
}
That way, $file holds the filename, and $_ holds each line.
>My second foreach loop then complains of my using uninitialised values. So
>I put in a print "@array_of_files\n"; after the first foreach loop.
>
>It's empty.
>
>OK, so while overwrote $_ but why does this delete the contents of
>@array_of_files?
Because $_ is an alias to the element in the array. Watch:
@n = (1 .. 3);
for (@n) {
$_ *= 2;
}
print "@n\n"; # 2 4 6
See? Now, when using while (<FILE>), Perl expands that to the more
"proper" while (defined($_ = <FILE>)). When the file is done being read,
<FILE> returns undef, and the loop stops. That means that $_ has been set
to undef, and since $_ is actually the element of the filename array,
you've just trashed that element.
>How do I stop while messing things up? Something to do with 'local' isn't
>it??
It could, but the better approach is to not use $_ in many different
environments at once.
--
Jeff "japhy" Pinyan [EMAIL PROTECTED] http://www.pobox.com/~japhy/
RPI Acacia brother #734 http://www.perlmonks.org/ http://www.cpan.org/
** Look for "Regular Expressions in Perl" published by Manning, in 2002 **
<stu> what does y/// stand for? <tenderpuss> why, yansliterate of course.
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