Re^4: File Reading and Closing confusion

I was referring to being wary when $line=<FH> is used on its own. To illustrate:

$ perl -e 'print "with_ending\nno_ending"' > a.txt
$ perl -MData::Dumper
    open(FH, "<", "a.txt") or die $!;
    my $line1 = <FH>;
    my $line2 = <FH>;
    my $line3 = <FH>;
    close FH;

    $Data::Dumper::Useqq = 1;
    print Dumper [$line1, $line2, $line3];
__END__
$VAR1 = [
          "with_ending\n",
          "no_end",
          undef
        ];
[download]

We see that there is a possibility that a line read ($line3 in this case) may return undef. That's what I meant: we need to be wary that a line read will not always return defined.

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Re^5: File Reading and Closing confusion by shmem (Chancellor) on Aug 09, 2010 at 09:30 UTC
I was referring to being wary when `$line=<FH>` is used on its own. Yes, but while takes care of that - and we/you were talking about a while loop, weren't you? 1. while (<>) { ... which is Perl short-hand for the more explicitly written version: 1. LINE: while (defined($line = <ARGV>)) { ... But of course, We see that there is a possibility that a line read ($line3 in this case) may return undef. - if you read past EOF, for instance. Then readline returns undef: `open(FH, "<", "a.txt") or die $!; my $line1 = <FH>; my $line2 = <FH>; print "eof!\n" if eof FH; my $line3 = <FH>; close FH; __END__ eof!` [download] That's what I meant: we need to be wary that a line read will not always return defined. That's exactly the condition when both the `while($line = <FH>) { }` and `while(defined($line = <FH>)) { }` loops terminate, so there's no difference in a while loop.	[reply] [d/l] [select]
Re^6: File Reading and Closing confusion by repellent (Priest) on Aug 09, 2010 at 15:37 UTC
Yes, but `while` takes care of that - and we/you were talking about a while loop, weren't you? Yes and no. I was talking about: `while (<FH>) { ... }` [download] VS `$line = <FH>; # on its own / not as while condition` [download] Given the OP's prelude, I really thought that the OP was referring to these two cases. Sorry for the confusion! :)	[reply] [d/l] [select]


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