What is Bash from the gnu bash manual at gnu.org

Bash is the shell
or command language interpreter
for the GNU operating system
The name is an acronym for the Bourne Again SHell
a pun on Stephen Bourne
the author of the direct ancestor of the current Unix shell sh
which appeared in the Seventh Edition Bell Labs Research version of Unix

Bash is largely compatible with sh and incorporates useful features from the Korn shell ksh and the C shell csh
It is intended to be a conformant implementation of the IEEE POSIX Shell and Tools portion of the IEEE POSIX specification
It offers functional improvements over sh for both interactive and programming use

While the GNU operating system provides other shells
including a version of csh
Bash is the default shell
Like other GNU software
Bash is quite portable
It curREntly runs on nearly every version of Unix and a few other operating systems
independently supported ports exist for MS-DOS OS/2 and Windows platforms


At its base
a shell is simply a macro processor that executes commands
The term macro processor means functionality where text and symbols are expanded to create larger expressions

A Unix shell is both a command interpreter and a programming language
As a command interpreter
the shell provides the user interface to the rich set of GNU utilities
The programming language features allow these utilities to be combined
Files containing commands can be created
and becom commands themselves
These new commands have the same status as system commands in directaries such as /bin
allowing users or groups to establish custom environments to automate their common tasks