Bash (Unix shell)

Bash (from the English Bourne again shell, pun "Born again" shell — "reborn" shell) - improved and upgraded variation of the Bourne shell command shell. One of the most popular modern versions of the UNIX command shell. It is especially popular in the Linux environment, where it is often used as a pre-installed command shell.

It is a command processor that works, as a rule, interactively in a text window. Bash can also read commands from a file called a script (or script). Like all Unix shells, it supports auto-completion of file and directory names, command output substitution, variables, control over the order of execution, branching and loop operators. Keywords, syntax and other basic features of the language were borrowed from sh. Other features, such as history, were copied from csh and ksh. Bash basically conforms to the POSIX standard, but with a number of extensions[4].

The name "bash" is an acronym from the English Bourne-again-shell ("another-command-shell-Born") and is a play on words: Bourne-shell is one of the popular varieties of the command shell for UNIX (sh), authored by Stephen Bourne (1978), improved in 1987 by Brian Fox. The surname Bourne (Born) echoes the English word born, meaning "born", hence: born-again-command shell.

In September 2014, a widely exploited Bashdoor vulnerability was discovered in bash.