Finding the intersection of two arrays is described in
perlfaq 4. The short version: use a hash.
So incorporating fruitures notes from above, here is my (
untested, since I do not have access to a suitable ftp server) try:
#!/usr/bin/perl -w
use strict;
use Net::FTP;
my $host = 'www.ftp.com';
my $user = 'anonymous';
my $pass = 'updatepuller@ftp.com';
my $remote_dir = '/pub/antivirus/NAV/signatures';
my $destination_dir = 'current-sig';
Here I read the contents of lastupdate.txt into the array
@lupd. If the file does not exist, @lupd will be left empty (no need for a special flag).
my @lupd = ();
if(-e "./lastupdate.txt") {
open(LASTUPDATE,"./lastupdate.txt")
or die "Error while opening lastupdate.txt ($!)";
chomp( @lupd = <LASTUPDATE> );
close(LASTUPDATE);
}
The following construct is called a
hash slice. It is described in more detail in
this page
my %haveit;
@haveit{ @lupd } = (1) x @lupd;
my $ftp = Net::FTP->new($host, Debug => 1);
$ftp->login($user,$pass);
$ftp->type("I");
my @listing = grep /x86\.exe$/i, $ftp->ls($remote_dir);
my @newupdate;
foreach my $file (@listing) {
The hash slice above produced a hash which maps every known filename to a true value. So if the file has already been downloaded, we can simply skip the download. When the download is unsuccessful, the file is skipped as well.
next if $haveit{ $file };
$ftp->get($file) or next;
push @newupdate, $file;
}
$ftp->quit;
open(NEWUPDATE,">>./lastupdate.txt")
or die "Couldn't open lastupdate.txt for appending ($!)";
print NEWUPDATE map "$_\n", @newupdate;
close(NEWUPDATE)
or die "Closing lastupdate.txt failed ($!)";
You might also want to think about locking if there is any chance that two instances of this program run at the same time.