Cpu Usage from Linux Then Using It in a Arithmetic Expression

CPU Usage from Linux then using it in a arithmetic expression

Bash arithmetic is integer only. It won't accept fractional numbers like 93.4.
You need to pipe the expression through bc.

joulesFinal=`echo $joules2 * $cpu | bc`

How to calculate sum of CPU usage of users who are not me

Here's a command that should do the trick:

ps ax -o pcpu:5,user --no-headers | tr -s ' ' | grep -v $(whoami) | cut -d' ' -f2 | (tr '\n' + ; echo 0; ) | bc

The ps command will list the CPU usages of every process alongside its owner. The tr will squeeze together multiple spaces, so the cut later on works as wanted. The grep will filter out processes owned by you. The cut command will select the first column, ie, the CPU usages. The tr will substitute new lines for plus signs, and finally bc will evaluate the resulting arithmetic expression.

Cheers.

Bash script checking cpu usage of specific process

The problem is that bash can't handle decimals. You can just multiply them by 100 and work with plain integers instead:

#!/bin/bash
declare -i app_pid
declare -i app_cpu
declare -i cpu_limit
app_name="top"
cpu_limit="5000"
app_pid=`ps aux | grep $app_name | grep -v grep | awk {'print $2'}`
app_cpu=`ps aux | grep $app_name | grep -v grep | awk {'print $3*100'}`
if [[ $app_cpu -gt $cpu_limit ]]; then
     echo "crap"
else
     echo "we're good"
fi

Keep in mind that CPU percentage is a suboptimal measurement of application health. If you have two processes running infinite loops on a single core system, no other application of the same priority will ever go over 33%, even if they're trashing around.

How to get percentage of processor use with bash?

Processor use or utilization is a measurement over time. One way to measure utilization in % is by computation over two successive reads of /proc/stat. A simple common bash script to compute the percentage is:

#!/bin/bash

# Read /proc/stat file (for first datapoint)
read cpu user nice system idle iowait irq softirq steal guest< /proc/stat

# compute active and total utilizations
cpu_active_prev=$((user+system+nice+softirq+steal))
cpu_total_prev=$((user+system+nice+softirq+steal+idle+iowait))

usleep 50000

# Read /proc/stat file (for second datapoint)
read cpu user nice system idle iowait irq softirq steal guest< /proc/stat

# compute active and total utilizations
cpu_active_cur=$((user+system+nice+softirq+steal))
cpu_total_cur=$((user+system+nice+softirq+steal+idle+iowait))

# compute CPU utilization (%)
cpu_util=$((100*( cpu_active_cur-cpu_active_prev ) / (cpu_total_cur-cpu_total_prev) ))

printf " Current CPU Utilization : %s\n" "$cpu_util"

exit 0

use/output:

$ bash procstat-cpu.sh
 Current CPU Utilization : 10

output over 5 iterations:

$ ( declare -i cnt=0; while [ "$cnt" -lt 5 ]; do bash procstat-cpu.sh; ((cnt++)); done )
 Current CPU Utilization : 20
 Current CPU Utilization : 18
 Current CPU Utilization : 18
 Current CPU Utilization : 18
 Current CPU Utilization : 18

Bash: wait until CPU usage gets below a threshold

wait_for_cpu_usage()
{
    current=$(mpstat 1 1 | awk '$12 ~ /[0-9.]+/ { print int(100 - $12 + 0.5) }')
    while [[ "$current" -ge "$1" ]]; do
        current=$(mpstat 1 1 | awk '$12 ~ /[0-9.]+/ { print int(100 - $12 + 0.5) }')
        sleep 1
    done
}

Notice it requires sysstat package installed.

How to obtain the number of CPUs/cores in Linux from the command line?

grep -c ^processor /proc/cpuinfo

will count the number of lines starting with "processor" in /proc/cpuinfo

For systems with hyper-threading, you can use

grep ^cpu\\scores /proc/cpuinfo | uniq |  awk '{print $4}'

which should return (for example) 8 (whereas the command above would return 16)

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