Sometimes the kernel hangs and I'd like to see if I can kill the math-kernel process without destroying my front-end session and losing the changes in my unsaved notebook!
In your aliases file (~/.zsh_aliases) add
alias a=alias a km='kill -9 `pidof WolframKernel`'
Reload your shell. Now, if the front-end is hanging and you can't quit the kernel but don't want to lose your unsaved notebook changes, simply open a shell and type
Presto, kernels killed!
On OSX, if you don't have the pidof command do
brew install pidof.