Bash (Shell)
GNU Bourne-Again SHell, first released June 8, 1989 by {{Brian Fox}} for the {{GNU Project}} as a free-software replacement for the {{Bourne shell}}; the default login shell on most Linux distributions and, historically, on macOS, maintained since 1990 by {{Chet Ramey}}.
Bash (Shell), the Bourne-Again SHell, is a Unix command-line shell and scripting language written for the GNU Project by Brian Fox and first released as version 0.99 on June 8, 1989. The name is a pun on Stephen Bourne's original Bourne shell (/bin/sh) from 1979: Bash was designed to be a drop-in-compatible free-software replacement for sh under the GNU General Public License. Chet Ramey has been the primary maintainer since 1990. Bash's syntax is a superset of the Bourne shell's, so most sh scripts run unmodified. On top of that base, Bash absorbed features from the Korn shell (command-line editing via Readline, history expansion, arithmetic evaluation, arrays) and from C shell (job control, brace expansion, the conditional). It implements the POSIX Shell standard when run as /bin/sh or with --posix, but normally exposes a much richer language including associative arrays (4.0, 2009), the more flexible parameter expansion forms covered in Useful Bash Parameter Expansion Patterns, coprocesses, process substitution via <(...) and >(...), here-strings, and a regex match operator =~. Major releases: 1.0 (1989), 2.0 (1996, restructured around Readline), 3.0 (2004, multibyte support), 4.0 (2009, associative arrays and ${var^^} case modification), 5.0 (2019, EPOCHSECONDS and other internal variables), 5.3 (July 2025). Bash is the default interactive shell on most Linux distributions and was the default on macOS from 10.3 (2003) through 10.14, when Apple switched to Zsh in 10.15 (Catalina, 2019) to avoid shipping GPL-3 code. The Shellshock vulnerability disclosed in September 2014 (CVE-2014-6271) was a notable security incident affecting Bash's environment-variable function import.