Print the total CPU usage in the terminal and updates its value every second.

cpu_usage.sh

#!/bin/bash
# Created by Paul Colby (http://colby.id.au)
# Further edited by Georgi Stoyanov (http://gstoyanov.com), no rights reserved ;)

PREV_TOTAL=0
PREV_IDLE=0

# Determinining the number of CPU cores
CPU_CORES=$(nproc --all)

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 "${CPU[@]}"; do
    (( "TOTAL=$TOTAL+$VALUE" ))
  done

  # Calculate the CPU usage since we last checked.
  (( "DIFF_IDLE=$IDLE-$PREV_IDLE" ))
  (( "DIFF_TOTAL=$TOTAL-$PREV_TOTAL" ))
  (( "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