Bash, one of the Unix shells, was written by Brian Fox for the GNU program in 1987. The first official version was released in 1989. It was originally planned to be used on the GNU operating system, but it runs on most Unix-like operating systems, including Linux and Mac OS X v10.4, using it as the default shell. It has also been ported to Cygwin and MinGW on Microsoft Windows, or DJGPP projects that can be used on MS-DOS. There are also ports on Novell NetWare and Andriod. After 1990, Chet Ramey became the main maintainer.
For subsequent compatible and open source versions of the Bourne shell, its name comes from a pun (Bourne again / born again): Bourne-Again SHell.
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This figure collates some grammar and special variables commonly used in bash programming, which can be quickly searched when forgotten, instead of turning over a book.