Bourne again shell

Bash

Screenshot of a Bash session
Original author(s)	Brian Fox
Initial release	June 8, 1989; 28 years ago (1989-06-08)
Stable release	4.4.12 / January 27, 2017; 5 months ago (2017-01-27)
Repository	git.savannah.gnu.org/cgit/bash.git
Written in	C
Operating system	Unix-like, macOS (system includes an older GNU GPL v2 version); current version available through third parties Windows (newer GNU GPL v3+ version)
Platform	GNU
Available in	Multilingual (gettext)
Type	Unix shell, command language
License	GNU GPL v3+
Website	www.gnu.org/software/bash/

Bash is a Unix shell and command language written by Brian Fox for the GNU Project as a free software replacement for the Bourne shell. First released in 1989, it has been distributed widely as the default login shell for most Linux distributions and Apple's macOS (formerly OS X). A version is also available for Windows 10.

Bash is a command processor that typically runs in a text window, where the user types commands that cause actions. Bash can also read and execute commands from a file, called a script. Like all Unix shells, it supports filename globbing (wildcard matching), piping, here documents, command substitution, variables, and control structures for condition-testing and iteration. The keywords, syntax and other basic features of the language are all copied from sh. Other features, e.g., history, are copied from csh and ksh. Bash is a POSIX-compliant shell, but with a number of extensions.