Linux Tip/Tricks continue...

To print unique IPs from squid access.log and sort them

awk '{print $3}' /var/log/squid/access.log.0 | sort -ut . -n -k 1,1 -k 2,2 -k 3,3 -k 4,4 | nl

This one doesn't sort but gives uniq ips with line number.

awk '{print $3}' /var/log/squid/access.log.0 | sort -u | nl

To put some text on every blank line

sed 's/^/some text/' urls > newfile

To kill the process

ps -ef | grep xterm | awk '{print $2}' | xargs kill -9

Check if the machine is live, useful for use in scripts.

if ping -c 1 mydomain.com >/dev/null 2>&1; then echo "live";else echo "dead";fi