i3status is a small program (about 1500 SLOC) for generating a status bar for
dzen2, xmobar or similar programs. It is designed to be very efficient by
issuing a very small number of system calls, as one generally wants to update
such a status line every second. This ensures that even under high load, your
status bar is updated correctly. Also, it saves a bit of energy by not hogging
your CPU as much as spawning the corresponding amount of shell commands would.