CPU core load graph script for your bar

Simple script to add a CPU core load to your favorite bar

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3 minute read

A while back I changed my bar from Polybar to i3bar with i3blocks. One of the things I missed about Polybar is its internal CPU module, which can produce a core load graph directly in your bar by adding the right ramp characters. In this post I’m sharing a simple POSIX shell script I’ve written that does the same and can be used with any text-based bar. Here is what it looks like:

CPU core load graph in my bar.

This is the script.

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#!/bin/sh

# Define array
ramp_arr=(▁ ▂ ▃ ▄ ▅ ▆ ▇ █)

sar -P ALL 1 1 | grep -E 'Average:\s+[0-9]+' | while read -r line ; do
    val=$(echo $line | awk '{cpu_usage=$3} END {printf "%0.2f", cpu_usage}')
    idx=`echo "scale=4; $val/14.3" | bc`
    intidx=$( printf "%.0f" $idx )
    printf "${ramp_arr[$intidx]}"
done
echo

We use the sar command to get the CPU readings for one second, and then select the relevant lines with grep. The result of sar -P ALL 1 1 is a data point taken over one second, plus the average at the end. This can be modified by changing the parameters. Below is the output with my i7-7700.

$  sar -P ALL 1 1
Linux 5.11.11-arch1-1 (hidalgo) 	13/04/21 	_x86_64_	(8 CPU)

09:26:25        CPU     %user     %nice   %system   %iowait    %steal     %idle
09:26:26        all     27.04      0.00     10.48      0.00      0.00     62.48
09:26:26          0     32.35      0.00      7.84      0.00      0.00     59.80
09:26:26          1     26.17      0.00     12.15      0.00      0.00     61.68
09:26:26          2     33.01      0.00     11.65      0.00      0.00     55.34
09:26:26          3     26.73      0.00      7.92      0.00      0.00     65.35
09:26:26          4     24.51      0.00      8.82      0.00      0.00     66.67
09:26:26          5     26.73      0.00      9.90      0.00      0.00     63.37
09:26:26          6     23.00      0.00     12.00      0.00      0.00     65.00
09:26:26          7     23.81      0.00     13.33      0.00      0.00     62.86

Average:        CPU     %user     %nice   %system   %iowait    %steal     %idle
Average:        all     27.04      0.00     10.48      0.00      0.00     62.48
Average:          0     32.35      0.00      7.84      0.00      0.00     59.80
Average:          1     26.17      0.00     12.15      0.00      0.00     61.68
Average:          2     33.01      0.00     11.65      0.00      0.00     55.34
Average:          3     26.73      0.00      7.92      0.00      0.00     65.35
Average:          4     24.51      0.00      8.82      0.00      0.00     66.67
Average:          5     26.73      0.00      9.90      0.00      0.00     63.37
Average:          6     23.00      0.00     12.00      0.00      0.00     65.00
Average:          7     23.81      0.00     13.33      0.00      0.00     62.86

We need the average lines for each of the 8 cores (highlighted in the snippet above), from 0 to 7. We select the relevant lines with grep -E 'Average:\s+[0-9]+'. This selects as many lines as cores. If you have more or less than 8, it should also work.

After that, we process each of these lines by taking the column number 3 (%user column, which contains the percentage of CPU utilization that occurred while executing at the user level) with awk, and we convert it to the ramp array ($ramp_arr) index with some math using bc. Finally, the ramp character is printed and we go on to the next core.

Here is the block as it appears in my i3blocks configuration file.

[cpulevels]
command=$LOCAL_DIR/cpu-levels
interval=repeat
color=#ffffff
border=#62ef3b
border_right=0
border_left=0
border_top=0
kborder_bottom=1
markup=pango

If you want to have a look at my other bar scripts, you can find them in this repository.

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