#! perl -slw use strict; use threads; sub worker { my( $filename, $target, $start, $end ) = @_; open my $fh, '<', $filename or die $!; seek $fh, $start, 0; <$fh> if $start > 0; ## discard first partial line my $count = 0; 1+index( <$fh>, $target ) and ++$count while tell( $fh ) < $end; return $count; } our $T //= 4; my( $filename, $target ) = @ARGV; my $fsize = -s $filename; my $chunksize = int( $fsize / $T ); my @chunks = map{ $_ * $chunksize } 0 .. $T-1; push @chunks, $fsize; my @threads = map{ threads->new( \&worker, $filename, $target, $chunks[ $_ ], $chunks[ $_+1 ] ) } 0 .. $T-1; my $total = 0; $total += $_->join for @threads; print "Found $total '$target' lines";