Bourne Again SHell

From Rosetta Code

bash (the "Bourne Again SHell") is the GNU implementation of a Unix shell which is intended to be compatible with the original UNIX shell (/bin/sh) by Stephen Bourne. bash was primarily written and is maintained by Brian Fox and Chet Ramey. The name follows an FSF (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 "associative arrays" and 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).