Internal Program Version: bash  5.3.9

Bash is an sh-compatible command interpreter that executes commands
read from standard input or from a file.  Bash incorporates useful
features from the Korn and C shells (ksh and csh).  Bash is intended to
be a conformant implementation of the IEEE Posix Shell and Tools
specification (IEEE Working Group 1003.2).

https://www.gnu.org/software/bash/bash.html