The Unix shell which was the default shell in macOS until 10.15
Bash was the default shell in macOS until 2019 when it was depreciated in lieu of zsh in macOS 10.15 Catalina.
Bash is a command processor, which means that the user inputs text commands at a prompt. Like the majority of Unix shells, it supports filename wildcarding, piping, here documents, command substitution, variables and control structures for condition-testing and iteration. Almost all of the syntax was copied from the sh shell. macOS comes with version 3, the current version (5) can be installed via Homebrew or MacPorts.
