Linux中如何计算特定CPU使用率

Total CPU time since boot = user+nice+system+idle+iowait+irq+softirq+steal

Total CPU Idle time since boot = idle + iowait

Total CPU usage time since boot = Total CPU time since boot - Total CPU Idle time since boot

Total CPU percentage = Total CPU usage time since boot/Total CPU time since boot * 100%

CPU percentage between t1 and t2 = (（total2-total1）-（idle2-idle1））/（total2-total1）* 100%

#!/bin/bash

# by Paul Colby (http://colby.id.au), no rights reserved ;)

PREV_TOTAL=0

PREV_IDLE=0

while true; do

  # Get the total CPU statistics, discarding the 'cpu ' prefix.

  CPU=(`sed -n 's/^cpu\s//p' /proc/stat`)

  IDLE=${CPU[3]} # Just the idle CPU time.

  # Calculate the total CPU time.

  TOTAL=0

  for VALUE in "${CPU[@]}"; do

    let "TOTAL=$TOTAL+$VALUE"

  done

  # Calculate the CPU usage since we last checked.

  let "DIFF_IDLE=$IDLE-$PREV_IDLE"

  let "DIFF_TOTAL=$TOTAL-$PREV_TOTAL"

  let "DIFF_USAGE=(1000*($DIFF_TOTAL-$DIFF_IDLE)/$DIFF_TOTAL+5)/10"

  echo -en "\rCPU: $DIFF_USAGE%  \b\b"

  # Remember the total and idle CPU times for the next check.

  PREV_TOTAL="$TOTAL"

  PREV_IDLE="$IDLE"

  # Wait before checking again.

  sleep 1

done