linemode

Linemode is a term used in computing to describe an input processing mode in which user input is collected and made available to a program only after a line delimiter, typically a newline, has been entered. In this mode, the terminal driver or input subsystem handles line editing, echo, and related controls before delivering the data to the application. Linemode contrasts with character mode or raw mode, where input is delivered to the program one character at a time as it is typed.

In Unix-like systems, linemode is associated with canonical or line mode input. When a terminal is in canonical mode, the kernel buffers input until a newline or end-of-file is received, applying line editing features such as backspace handling and line-kill operations. Echoing of typed characters can be controlled separately. This line-oriented behavior is typical for command-line interfaces and shells, which read full lines of input before processing commands.

Linemode also appears in network and terminal protocols. Some interactive protocols offer a mode where input can be processed per character, and others where input is transmitted line by line. In certain contexts, linemode may involve negotiation between client and server to determine how keystrokes are transmitted and interpreted, potentially affecting local editing features and the handling of special characters or signals.

Limitations of linemode include reduced interactivity for programs that rely on real-time, per-character input, such as text editors or games. Such applications often switch to character or raw mode to capture input immediately. Modern systems typically provide mechanisms to switch between modes, enabling both line-oriented and character-oriented interaction as needed.