The Interactive Shell

The POSIX shell is a powerful and widely used interface in Unix-like operating systems. It serves as a fundamental tool for interacting with the operating system, allowing users to execute commands,to manage the system and automate tasks. The POSIX shell’s design is rooted in simplicity and accessibility, as it operates on a word and line basis, making it inherently human-readable. Its interactive nature enables users to input commands and receive immediate feedback, facilitating efficient system navigation and execution of operations.

The shell command language originally began as a simple word-based human-interactive language consisting of a series of commands as lines of input. As time went on, additional programmatic features were added to provide control flow over groups of commands. These additional features are intended primarily to be used in shell scripts, rather than in an interactive environment. In this module, we will focus only on the primarily interactive subset of the language. In the next module, we will study the programmatic features of the language in order to write more complex shell script programs.