Bash

The default shell on most Linux distributions.

Bash (Bourne Again Shell) is the shell most Linux systems start you in, and the language most shell scripts are written in. It combines an interactive command line: history, completion, job control, with a full scripting language: variables, conditionals, loops, functions.

Scripts usually declare it on the first line with the shebang #!/bin/bash. Bash is deliberately compatible with the older Bourne shell (sh), which is why portable scripts often target sh instead. macOS switched its default interactive shell to zsh, but bash remains the lingua franca of servers and automation.

See it in practice

$ echo $BASH_VERSION

Confirms you are in bash and which version. Scripts that rely on newer features should check this rather than assume.

Where you'll meet it

Shell

The program that reads your commands and runs them.

Shebang (#!)

The first line telling the system which interpreter runs a script.

Bash scripting for beginners

In-depth guide

Learn these concepts by typing them: the interactive course builds them up lesson by lesson in a real simulated shell.