This is the scripts that creates the bar in my herbstluftwm setup. It's written in rc (the plan9 shell) because why not.
#!/usr/bin/env rc monitor=$1 . ./lib hc pad $monitor $panel_height fn process { awk -f process.awk \ -v selbg=$"selbg \ -v selfg=$"selfg \ -v font=$"font \ -v monitor=$"monitor } fn render { dzen2 -w $panel_width -x $x -y $y -h $panel_height \ -fn $"font -ta l -bg $"bgcolor -fg '#222222' } ./event-gen $"monitor | process | render >[2] /dev/null