This chapter describes the use of the pseudoterminal driver (FTDRIVER) and the pseudoterminal software.

A pseudoterminal is a software device that appears as a real terminal to an application communicating with it, but does not require the existence of a physical terminal. A pseudoterminal consists of two components: the pseudoterminal device and a control program. The control program acts like a keyboard; that is, anything written to the control program appears on the pseudoterminal device as if the keystrokes had been typed in at a physical terminal. The control program also acts like a viewport to the pseudoterminal device; that is, the control program reads anything that is written by the system to the pseudoterminal device.

A pseudoterminal allows an application to be set up on the control side of the link to communicate with another application that is on the pseudoterminal side. This arrangement allows development of applications that either simulate users or monitor the communication between a real user (at a physical terminal) and an application. As with other devices, the work of the pseudoterminal is performed by a device driver and is tightly coupled to the operating system.

The pseudoterminal driver software includes a set of control connection routines. Applications can use these routines to perform pseudoterminal operations and functions. Appendix D provides the calling conventions for these routines.