Vty

Vty, often written as VTY in documentation, is a term used in computing to refer to several related concepts. It most commonly denotes either virtual terminal lines used for remote device management or the Haskell library that implements terminal handling for text-based user interfaces. The dual usage can lead to confusion without context.

In networking, Virtual Teletype (VTY) lines provide remote access to network devices such as routers and switches. They are logical input/output consoles that allow multiple simultaneous sessions over a network, typically via Telnet or SSH. On devices like those running Cisco IOS, administrators enable and configure VTY lines with commands such as line vty 0 4, and set authentication and transport methods using statements like login, login local, transport input ssh, or transport input telnet. Management characteristics include session timeouts, access control, and privilege level settings, all aimed at secure remote administration.

In software development, vty refers to a Haskell library that implements terminal handling for text-based user interfaces. The library provides low-level support for rendering to the terminal, processing input events, and applying colors and text attributes, using ANSI escape codes and compatible terminal features. It serves as a backend foundation for building TUIs and is commonly used in conjunction with higher-level libraries such as Brick. The vty library emphasizes portability across terminal emulators and supports Unicode input and output, making it suitable for cross-platform terminal applications.