wiki/sh

sh

https://en.wikipedia.org/wiki/Shell_(computing)
In computing, a shell is a user interface for access to an operating system's services. In general, operating system shells use either a command-line interface (CLI) or graphical user interface (GUI), depending on a computer's role and particular operation. It is named a shell because it is the outermost layer around the operating system.[1] [2]

''Rich’s sh (POSIX shell) tricks''
https://www.etalabs.net/sh_tricks.html

Discussion on Lobsters
https://lobste.rs/s/uk5esr/rich_s_sh_posix_shell_tricks