Get CPU usage in shell script?

Use top -b (and other switches if you want different outputs). It will just dump to stdout instead of jumping into a curses window.

The most useful tool I've found for monitoring a server while performing a test such as JMeter on it is dstat. It not only gives you a range of stats from the server, it outputs to csv for easy import into a spreadsheet and lets you extend the tool with modules written in Python.

User load: top -b -n 2 |grep Cpu |tail -n 1 |awk '{print $2}' |sed 's/.[^.]*$//' System load: top -b -n 2 |grep Cpu |tail -n 1 |awk '{print $3}' |sed 's/.[^.]*$//' Idle load: top -b -n 1 |grep Cpu |tail -n 1 |awk '{print $5}' |sed 's/.[^.]*$//'

Every outcome is a round decimal.