uniload displays the load per CPU core of your system. It reads /proc/stat, calculates the share of time each core was busy doing something (including iowait), and prints a unicode block character for each core.

(NB: the font on GitHub seems to be suboptimal. Using the Terminus font, the bottoms of the blocks are perfectly aligned.)

$ uniload
▃▄▅▃%

It takes only one optional parameter, the delay between reading /proc/stat, which by default is 1000ms. The minimum is 100ms, passing anything less than that will result in a 100ms delay:

# using 500ms delay
$ uniload 500
█▁▁▁% 

It's Rust, so get Rust via either https://rustup.rs/ or your distribution's package manager. Then, use cargo build --release, and find the uniload binary in ./target/release/. Copy the binary to somewhere in your $PATH.

The simple output allows you to use it in text-based status bars. I'm using this in my i3blocks and tmux status bars.

Add to your i3blocks.conf:

[uniload]
interval=5

And place/symlink uniload in your i3blocks directory.

This highly depends on your own .tmux.conf of course, but as an example from mine:

set-option -g status-right '#(uniload) #(uptime | sed "s/.*average: //" | sed s/,//g) | #[fg=bold]%H:%M:%S #[default]'