perl parp parp

I updated the IP address for both my Name Servers tonite, and was monitoring to see how quickly the new addresses were propagating. First stop was the exceptionally useful Whats My DNS

At the host level I also wanted to track the incoming DNS queries using tcpdump. I could see them streaming into the new host, and visually you could see an obvious difference when viewing the output of the same command on the old host. I googled around for a timer utility which run a command for a given time, so i could quantify the difference. Perfect answer was here, a simple perl wrapper function.

Here's how to use it to run tcpdump command for sixty seconds, and count the packets seen:

# doalarm () { perl -e 'alarm shift; exec @ARGV' "$@"; }
# doalarm 60 tcpdump -u -i eth0 port 53 -n |wc -l
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 65535 bytes