If you ever tried to work with Linux command line, ls command was surely one of the first commands you have executed. In fact, ls command is so frequently used, that its name is often considered as the best choice to name a Trojan Horse. Even though you use ls command on daily basis, its wast number of options always makes you to reach for ls's manual page. Doing so you learn something new every time you open ls's manual page . This guide will try to do the same. ls command belongs to a group of core utilities on your Linux system. GNU ls was written by Stallman and David MacKenzie based on the original AT&T code written in the 60s.