CPU usage in Percentage

HZ=`awk '/\\#define HZ/ {print $3}' /usr/include/asm-generic/param.h`; NUMCPUS=`grep ^proc /proc/cpuinfo | wc -l`; FIRST=`cat /proc/stat | awk '/^cpu / {print $5}'`; sleep 1; SECOND=`cat /proc/stat | awk '/^cpu / {print $5}'`; USED=`echo 4 k 100 $SECOND $FIRST - $NUMCPUS $HZ \\* / 100 \\* - p | dc`; echo ${USED}