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This is an excerpt from the latest version perlfaq5.pod, which
comes with the standard Perl distribution. These postings aim to
reduce the number of repeated questions as well as allow the community
to review and update the answers. The latest version of the complete
perlfaq is at http://faq.perl.org .

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5.3: How do I count the number of lines in a file?

(contributed by brian d foy)

Conceptually, the easiest way to count the lines in a file is to simply
read them and count them:

my $count = 0;
while( <$fh> ) { $count++; }

You don't really have to count them yourself, though, since Perl already
does that with the $. variable, which is the current line number from
the last filehandle read:

1 while( <$fh> );
my $count = $.;

If you want to use $., you can reduce it to a simple one-liner, like one
of these:

% perl -lne '} print $.; {' file

% perl -lne 'END { print $. }' file

Those can be rather inefficient though. If they aren't fast enough for
you, you might just read chunks of data and count the number of
newlines:

my $lines = 0;
open my($fh), '<:raw', $filename or die "Can't open $filename: $!";
while( sysread $fh, $buffer, 4096 ) {
$lines += ( $buffer =~ tr/\n// );
}
close FILE;

However, that doesn't work if the line ending isn't a newline. You might
change that "tr///" to a "s///" so you can count the number of times the
input record separator, $/, shows up:

my $lines = 0;
open my($fh), '<:raw', $filename or die "Can't open $filename: $!";
while( sysread $fh, $buffer, 4096 ) {
$lines += ( $buffer =~ s|$/||g; );
}
close FILE;

If you don't mind shelling out, the "wc" command is usually the fastest,
even with the extra interprocess overhead. Ensure that you have an
untainted filename though:

#!perl -T

$ENV{PATH} = undef;

my $lines;
if( $filename =~ /^([0-9a-z_.]+)\z/ ) {
$lines = `/usr/bin/wc -l $1`
chomp $lines;
}



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