Using alarm to set a timeout

[droid99]

I am using the following code to read in a web site access log file and translate IP addresses to their domain names:

1 open(LOG, "$logfile");
2 open(TEMP, ">$tempfile");
3 while(my $line = <LOG>)
4 {
5 if($line =~ /^(\d{2,}\.\d{2,}\.\d{2,}\.\d{2,})/)
6 {
7 my $ip_address = $1;
8 unless (exists $hostname{$ip_address})
9 {
10 $hostname{$ip_address} = gethostbyaddr
(inet_aton($ip_address), AF_INET);
11 print TEMP "$ip_address -> $hostname{$ip_address}\n";
12 }
13 }
14 }
15 close TEMP;
16 close LOG;


Here is my question: Line 10 can take a long time to process just one IP address to domain name lookup. How can I use alarm to set a timeout after 1 second has passed?

Thank you very much for any help.

 

[TrojanWarBlade]

1  open(LOG, "$logfile");
2  open(TEMP, ">$tempfile");
3  while(my $line = <LOG>)
4  {
5      if($line =~ /^(\d{2,}\.\d{2,}\.\d{2,}\.\d{2,})/)
6      {
7          my $ip_address = $1;
8          unless (exists $hostname{$ip_address})
9          {
10             eval {
11               local $SIG{ALRM} = sub { die "alarm clock restart" };
12               alarm 10;
13               $hostname{$ip_address} = gethostbyaddr
                     (inet_aton($ip_address), AF_INET);
14               alarm 0;
15             };
16             if ($@ and $@ !~ /alarm clock restart/) { die }
17             print TEMP "$ip_address -> $hostname{$ip_address}\n";
18         }
19     }
20 }
21 close TEMP;
22 close LOG;

You can obviously change the "die" on line 16 to do whatever you want it to do on timeout.

Trojan