poll/monitor a linux command's output

Question

Is there a way to monitor the output of a linux command without having to type it over and over.

I want to do something like:

tail -f file.txt

But for a command like:

ps aux | grep httpd | wc

Thanks!

Answer 1

watch 'ps aux | grep httpd | wc'

Answer 2

while true
do
  ps aux | grep httpd | wc
  sleep 10
done