Про grep и не только -> youtube.com
Where did the “wheel” group get its name.
Экскурс в историю от дедка maddog-a.
crontab наглядно -> crontab.guru
"It's interesting that the common Unix command grep was actually inspired by this ex command (and is named after the way in which it was documented). The ex command :g/re/p (grep) was the way they documented how to "globally" "print" lines containing a "regular expression" (re)."
Экскурс в историю, откуда взялся select и почему -> idea.popcount.org