Bourne Again SHell

bash (the "Bourne Again SHell") is the GNU implementation of a Unix shell which is intended to be compatible with the original UNIX Bourne Shell (/bin/sh) by Stephen R. Bourne. bash was primarily written and is maintained by Brian Fox and Chet Ramey. The name follows a Free Software Foundation tradition for whimsical and pun-referential names.

In functionality bash goes well beyond the original Bourne shells and closely matches the extensions of David Korn's "Korn shell" (ksh) but lacks built-in support for co-processes. However, bash also adds a number of interactive features drawn from Bill Joy's C shell (including the many "bang expansion operators" for things like !! (expand to entire previous command), !-2 (expand to penultimate command), !$ (expand to last argument of previous command) etc).