Package bash4: Information

Bash is an sh-compatible command language interpreter that executes
commands read from the standard input or from a file.  Bash also
incorporates useful features from the Korn and C shells (ksh and csh).
Most sh scripts can be run by bash without modification.

Bash is ultimately intended to be a conformant implementation of the
IEEE POSIX Shell and Tools specification (IEEE Working Group 1003.2).