High Quality Content by WIKIPEDIA articles! Bash is a Unix shell written by Brian Fox for the GNU Project as a free software replacement for the Bourne shell (sh). Released in 1989, it has been distributed widely as the shell for the GNU operating system and as the default shell on Linux, Mac OS X and Darwin. It has been ported to Microsoft Windows and distributed with Cygwin and MinGW, to DOS by the DJGPP project and to Novell NetWare.