If you want to minimize memory usage, you will have to suffer in speed somewhere, somehow. There is a trade off that you have to make.
I think one of the easiest method is to use a proper database to record your files, like MySQL, Postgres, Oracle, etc. Create a table with an *index* on the filename to speed up SQL query. Let the database do the search optimization for you.
#!/usr/local/bin/perl -w
use strict;
use DBI;
use DBD::Sybase;
use File::Find;
my $dbh = ....; # connect to database
my $sth = $dbh->prepare("select filename from bench where filename=?")
+;
# look for new files
my @new_files;
find( { follow => 1, no_chdir => 1,
wanted =>
sub {
if (! /\.$/) { # ignore unwanted . or ..
$sth->execute($_);
my $file_exists;
while (my @res = $sth->fetchrow_array()) { $file_exists+
++ }
push @new_files if !$file_exits;
}
}
}, '/');
$sth->finish;
# insert new files into the database
$sth = $dbh->prepare("insert into bench (filename) values (?)");
$sth->execute($_) for @new_files;
$sth->finish;
# do stuff with @new_files ....
I can think of another solution, although the performance in speed is not great, that uses resonable amount of memory.
#!/usr/local/bin/perl -w
use strict;
use File::Find;
my $bench_file = 'bench.txt';
my @new_files;
find( { follow => 1, no_chdir => 1,
wanted => \&callback }, '/');
sub callback {
if (! /\.$/) { # ignore unwanted . or ..
if ( ! `grep '$_' $bench_file` ) {
push @new_files, $_; # remember this file
}
}
}
# append unseen filenames to bench.txt file
open BENCH, ">>bench.txt"
or die "Can not append to bench.txt";
print BENCH "$_\n" foreach (@new_files);
close BENCH;