linux shell: How to read command argument from a file?

Question

I have process id in a file "pid" I'd like to kill it.

Something like:

kill -9 <read pid from file>

I tried:

kill -9 `more pid` 

but it does not work. I also tried xargs but can't get my head around it.

Answer 1

Does

kill -9 $(cat pid)

work for you?

Answer 2

Let me summarize all answers

kill -9 $(cat pid)
kill -9 `cat pid`
cat pid | xargs kill -9