[1] Fast, small, and virtually compatible[citation needed] with the POSIX standard's specification of the Unix shell, ash did not provide line editing or command history mechanisms, because Almquist felt that such functionality should be moved into the terminal driver.

[2] These derivatives of ash are installed as the default shell (/bin/sh) on FreeBSD, NetBSD, DragonFly BSD, MINIX, and in some Linux distributions.

[citation needed] Line editing and history support based on GNU Readline is optional (--with-libedit).

[6] A result of the shift is that many shell scripts were found making use of Bash-specific functionalities ("bashisms") without properly declaring it in the shebang line.

As a result, Debian policy was amended to allow script developers to assume a largely POSIX-compliant shell, save for the extensions merged into Dash for convenience (local, echo -n, test -a / -o).

Many vendors of commercial systems also include it, because it is not GPL-Ware, but has a licence that allows it, for example on Sophos XGs it is misleadingly called "Advanced Shell".