How to kill all processes matching a name?

The safe way to do this is:

pkill -f amarok

ps aux | grep -ie amarok | awk '{print $2}' | xargs kill -9 

xargs(1): xargs -- construct argument list(s) and execute utility. Helpful when you want to pipe in arguments to something like kill or ls or so on.

use pgrep

kill -9 $(pgrep amarok)

From man 1 pkill

-f     The pattern is normally only matched against the process name.
       When -f is set, the full command line is used.

Which means, for example, if we see these lines in ps aux:

apache   24268  0.0  2.6 388152 27116 ?        S    Jun13   0:10 /usr/sbin/httpd
apache   24272  0.0  2.6 387944 27104 ?        S    Jun13   0:09 /usr/sbin/httpd
apache   24319  0.0  2.6 387884 27316 ?        S    Jun15   0:04 /usr/sbin/httpd

We can kill them all using the pkill -f option:

pkill -f httpd