Bourne-Again shellBash is a Unix command shell written for the GNU project. Its name is an acronym for "Bourne-Again SHell": a pun on the Bourne shell sh, which was the original Unix shell. The Bash command syntax is largely backward-compatible with sh, and includes ideas drawn from ksh and csh, such as the command history, the directory stack, the $RANDOM variable, and the POSIX form of command substitution, '$('.
The original Bourne shell was written by Stephen Bourne. Bash was primarily written by Brian Fox and Chet Ramey.