Then there is a lot of history that you do not know, starting with BSD and progressing through the late 1980s and early 1990s when there was a torrent of "clone

Then there is a lot of history that you do not know, starting with BSD and progressing through the late 1980s and early 1990s when there was a torrent of "clones" of things. The "Vixie cron" that you might even still be using is a "PD" clone of the Unix cron program, reimplemented from scratch with the same name. The van Smoorenburg "init" that you might have heard of was a clone of (an at the time sadly already out of date) Unix init program. All of the stuff in GNU coreutils and other similar GNU toolsets was a deliberate reimplementation from scratch. And then there are the Thompson, Mashey, Bourne, Almquist, Bourne Again, Korn, Z, and Watanabe shells. And BusyBox and ToyBox. And /usr/lib/sendmail . And the "mailx" utility. And "awk". And "vncviewer". And "getty". And so on. * https://unix.stackexchange.com/a/508142/5132 https://unix.stackexchange.com/a/508142/5132 * http://jdebp.uk./FGA/inittab-getty-is-history.html http://jdebp.uk./FGA/inittab-getty-is-history.html * https://news.ycombinator.com/item?id=19988382 https://news.ycombinator.com/item?id=19988382 * https://news.ycombinator.com/item?id=17005677 https://news.ycombinator.com/item?id=17005677 * https://unix.stackexchange.com/a/316279/5132 https://unix.stackexchange.com/a/316279/5132