Terminalhandling

Terminal handling refers to the management of input and output between user processes and terminal devices or terminal emulators. In computing, a terminal can be a physical device or a software interface (a pseudo-terminal). The operating system provides a terminal driver and a line discipline that translate byte streams into characters and interpret control sequences.

Terminal devices and sessions: Terminals are represented by device files such as /dev/tty, /dev/ttyS*, or /dev/pts/* for pseudo-terminals. Each process or set of processes can have a controlling terminal and belong to a session; signals like Ctrl-C are delivered to the foreground process group. Pseudo-terminals are widely used by terminal emulators and remote sessions (such as SSH).

Modes and attributes: Terminal behavior is configurable via the termios interface. Canonical mode buffers input until a newline or an erase character; noncanonical (raw) mode passes input immediately. Echoing, signal handling, flow control, and special character processing are configurable. Attributes can be read and updated with tcgetattr and tcsetattr, and window size is queried with TIOCGWINSZ.

Databases and capabilities: Applications rely on terminfo or termcap databases to query terminal capabilities (such as cursor movement, color support, and screen size). Libraries like ncurses and Readline implement higher-level editing and display by using these capabilities.

Usage and tools: Shells use terminal handling for job control and interactive editing; terminal multiplexers and remote shells rely on pseudo-terminals to multiplex sessions. Terminal emulators provide a virtual terminal interface to the user while communicating with the kernel.

Security and control: The controlling terminal governs access for job control and signal delivery, making proper terminal handling essential for interactive programs, scripting, and remote access.