cpu.sh

#!/bin/bash
#
# Output the CPU usage of a specified PID every so often.
#  function 'u' from StackExchange, rest by Riley Hunt.
#
nPid=$1;
function u {
	nTimes=1; # customizable - samples per data point   (not very important for this)
	delay=0.1; # customizable - interval between samples (not very important for this)
	strCalc=`top -d $delay -b -n $nTimes -p $nPid \
	  |grep $nPid \
	  |sed -r -e "s;\s\s*; ;g" -e "s;^ *;;" \
	  |cut -d' ' -f9 \
	  |tr '\n' '+' \
	  |sed -r -e "s;(.*)[+]$;\1;" -e "s/.*/scale=2;(&)\/$nTimes/"`;
	nPercCpu=`echo "$strCalc" |bc -l`  # fancy formatting stuff to get what's in the CPU column of the TOP output
	echo $nPercCpu
}

for i in {1..500} # just press ctrl+c to interrupt when you feel like it
do
	echo `u` # print cpu usage of process (which is the output of the function 'u')
	sleep 4 # customizable - seconds to sleep between each data point
done