CLIs

CLIs, or command-line interfaces, are text-based user interfaces that allow people to interact with computer programs by typing commands at a prompt. Unlike graphical interfaces, CLIs rely on text input and output, with commands conveying actions and results appearing as text. Commands typically consist of a program name, subcommands, options (flags), and arguments.

Structure and usage: A typical CLI command includes a primary action, optional flags, and one or more operands. Examples: ls -l /home lists entries in long format; git commit -m "message" records a snapshot with a message. CLIs often support piping and redirection, where the output of one command becomes the input of another, or is written to a file.

History and environments: CLIs originated in early command interpreters and batch systems, with modern shells such as Bash, Zsh, Fish, and PowerShell providing line editing, history, completion, scripting, and environment management. They operate in various environments, including Unix-like systems, Windows, and embedded platforms.

Design, benefits, and limitations: CLIs favor scriptability, automation, resource efficiency, and precise control for administration and automation tasks. They require learning a command vocabulary and consistent conventions, but can be more efficient for repetitive workflows. Common features include help output, aliases, tab completion, and piped I/O for composing tools.

Applications and examples: CLIs underpin system administration, software development, package managers, version control, cloud and container tooling, and data processing pipelines. Widely used CLIs include git, Docker, kubectl, npm, and package managers such as apt and Homebrew. They remain foundational even as graphical interfaces evolve.