Bash is an interactive command interpreter and a scripting language. It reads a line of text, splits it into a program name and arguments, starts that program, and shows you stdout and stderr.
Core characteristics
- POSIX heritage — builds on the Bourne shell (
sh) with extensions - Text in, text out — values are strings unless you use arithmetic expansion
- Composition — small tools connected with pipes and redirection
- Ubiquitous — default on many Linux distros; macOS often uses zsh as login shell but Bash remains common in scripts
Interactive vs script
# Interactive: type at the prompt
$ echo "Hello from Bash"
Hello from Bash
# Script: save to hello.sh, make executable, run
echo "Hello from Bash"Interactive mode is great for exploration. Scripts make tasks repeatable—essential for CI and server maintenance.
Where Bash appears
CI pipelines, Docker entrypoints, server maintenance, Makefiles, and local dev scripts. Pair with Git for hooks and Tools for terminal setup.
Important interview questions and answers
- Q: Is Bash only for Linux?
A: No—macOS, WSL on Windows, and containers all use Bash or Bash-compatible shells. - Q: Bash vs Python for automation?
A: Bash excels at calling existing CLI tools and file operations; Python excels at complex logic and libraries—teams use both.
Self-check
- What extension do Bash scripts often use?
- Name one production place Bash runs besides your laptop.
Tip: Run bash --version locally; macOS may ship an older Bash while scripts in CI use newer GNU Bash.
Interview prep
- Interactive vs script?
Interactive runs line by line; scripts batch commands for repeatability and CI.
- What does a shebang do?
Tells the OS which interpreter executes the file when run as a program.