Display CPU usage in percentage

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 2 k 100 $SECOND $FIRST - $NUMCPUS / - p | dc`; echo ${USED}% CPU Usage
Using the output of 'ps' to determine CPU usage is misleading, as the CPU column in 'ps' shows CPU usage per process over the entire lifetime of the process. In order to get *current* CPU usage (without scraping a top screen) you need to pull some numbers from /proc/stat. Here, we take two readings, once second apart, determine how much IDLE time was spent across all CPUs, divide by the number of CPUs, and then subtract from 100 to get non-idle time.
Sample Output
1.84% CPU Usage

0
By: toxick
2012-10-02 03:57:51

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What Others Think

Granted this only works on devices where HZ=100. Alternatively, this may work for other systems: 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}% CPU Usage Deriving HZ from the include files.
toxick · 315 weeks ago

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