Trying to Get Total CPU Usage in Bash

Question

I'm trying to get the CPU's total load with this:

IDLE=$(mpstat | grep "all" | cut -c 92-)

CPULD=$(expr 100 - $IDLE)

echo $CPULD

but it always returns:

expr: non-integer argument on the second line. 

I've looked around and everyone says that integers will be automatically recognized in strings, but it doesn't seem to be working.

EDIT: For those of you who wish to see my full and now-working script, it is here: http://pastebin.com/cFQzz4Up

Answer 1

bash (and expr) can not do floating point arithmetics, you need to take help of bc.

For example :

$ IDLE=$(mpstat | grep "all" | cut -c 92-)

Lets say $IDLE is 77.25.

Now you need bc :

$ IDLE=77.25

$ CPULD="$(bc <<<"100 - $IDLE")"

$ echo "$CPULD"
22.75

bc operates on files, so we can pass the manipulation string via STDIN, although i prefer here strings :

$ echo "100 - 45.34" | bc
54.66

$ bc <<<"100 - 45.34"
54.66

On a different note, to get the IDLE % of CPU, instead of mpstat | grep "all" | cut -c 92- you can do :

mpstat | grep -Po 'all.* \K[^ ]+$'

Answer 2

I came up with this solution and it works for me.

echo print `top -n 1 | tr -s " " | cut -d$" " -f10 | tail -n +8 | head -n -1 | paste -sd+ | bc`/ `nproc` | python

Source (write up): https://mohammadg.com/programming/how-to-get-overall-cpu-utilization-from-the-bash-command-line/

Answer 3

Use the command uptime. It gives system load averages for the past 1, 5, and 15 minutes (man page).

# 1. get total average CPU usage for the past minute
avg_cpu_use=$(uptime)
# 2. split response
IFS=',' read -ra avg_cpu_use_arr <<< "$avg_cpu_use"
# 3. find cpu usage
avg_cpu_use=""
for i in "${avg_cpu_use_arr[@]}"; do :
    if [[ $i == *"load average"* ]]; then
        avg_cpu_use=$i
        break       
    fi
done
# 4. create response
avg_cpu_use=$(echo ${avg_cpu_use:16})   # Remove "  load average: "
if [[ -z "${avg_cpu_use// }" ]]; then
    avg_cpu_use="CPU: N/A perc used"
    exit -1
else
    avg_cpu_use="CPU: ${avg_cpu_use} perc used"
fi