High Quality Content by WIKIPEDIA articles! The Almquist shell (also known as A Shell, ash and sh) was originally Kenneth Almquist`s clone of the SVR4-variant of the Bourne shell; it is a fast, small, POSIX-compatible Unix shell designed to replace the Bourne shell in later BSD distributions. Originally it did not feature line editing or command history mechanisms, because Almquist felt that such should be moved into the terminal driver; however, current variants support it.