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I am trying to figure out how to extract the cpu core utilization for a SINGLE process in linux and parse it. I know that I can get the overall core utilization via top and then press "1". I am already able to parse that. However, now I want to do the same thing for a single process. I tried it with ps and calculating the core utilization myself but I am not so sure if my script is accurate enough, something seems off. (Note that this version calculates overall core utilization since it is WIP) I get errors like this after a while in my terminal:

test.sh: line 31: +: syntax error: operand expected (error token is "+")

I cannot figure out why this error just randomly occurs.

#!/bin/env bash
read -p "Enter PID to observe:" pid
run=false
ps -p $pid -L -o cputime,etime,psr,pcpu

for (( u = 1 ; u <= 100 ; u++ ))
do

lines=$(ps -p $pid -L -o psr,pcpu | awk 'END{print NR}')


    for (( i=1; i<=$lines; i++))
    do


        core=$(ps -p $pid -L -o psr,pcpu | awk 'NR=='$i'{print $1}')

        if [ $run == false ]

            then cpuTimeS=+$(ps -p $pid -L -o cputime,etime | awk 'NR=='$i'{print $1}' | awk -F : '{ printf("%.2f\n", $1*60+$2*60+$3); }')
            elapsedTimeS=+$(ps -p $pid -L -o cputime,etime | awk 'NR=='$i'{print $2}' | awk -F : '{ printf("%.2f\n", $1*60+$2*60+$3); }')

            cpuTimeSi=${cpuTimeS%.*}        
            elapsedTimeSi=${elapsedTimeS%.*}

            cpuTimeSiResult=$(( cpuTimeSi + cpuTimeSiResult ))
            elapsedTimeSiResult=$(( elapsedTimeSi + elapsedTimeSiResult ))

            else
            cpuTimeE=+$(ps -p $pid -L -o cputime,etime | awk 'NR=='$i'{print $1}' | awk -F : '{ printf("%.2f\n", $1*60+$2*60+$3); }')
            elapsedTimeE=+$(ps -p $pid -L -o cputime,etime | awk 'NR=='$i'{print $2}' | awk -F : '{ printf("%.2f\n", $1*60+$2*60+$3); }')

            cpuTimeEi=${cpuTimeE%.*}        
            elapsedTimeEi=${elapsedTimeE%.*}

            cpuTimeEiResult=$(( cpuTimeEi + cpuTimeEiResult ))
            elapsedTimeEiResult=$(( elapsedTimeEi + elapsedTimeEiResult ))

        fi  
done

if [ "$run" = true ]

        then result=$( echo "scale=2; ($cpuTimeEiResult - $cpuTimeSiResult) / ($elapsedTimeEiResult - $elapsedTimeSiResult) * 100.0" | bc)
        echo "RESULT:" $result
        echo "cpuTimeSTART:" $cpuTimeSiResult
        echo "elapsedTimeSTART:" $elapsedTimeSiResult
        echo "cpuTimeEND:" $cpuTimeEiResult
        echo "elapsedTimeEND:" $elapsedTimeEiResult

fi

sleep 1

if [ "$run" = false ]
    then run=true
else
    run=false
fi



done

Are there any ideas on how I could solve this better?

I am glad for any advice

user2856188
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1 Answers1

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Looking at your actual request to get the CPU utilization from a particular process; this could be done in less lines; e.g. below is the CPU usage after giving a seq command.

#using the process name
$ ps -C seq -o %cpu
%CPU
10.4

#using the process id
$ ps -p 5710 -o %cpu
%CPU
10.4
Kokkie
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