18.1. Introduction

The handling of terminal I/O is a messy area, regardless of the operating system. The UNIX System is no exception. The manual page for terminal I/O is usually one of the longest in most editions of the programmer's manuals.

With the UNIX System, a schism formed in the late 1970s when System III developed a different set of terminal routines from those of Version 7. The System III style of terminal I/O continued through System V, and the Version 7 style became the standard for the BSD-derived systems. As with signals, this difference between the two worlds has been conquered by POSIX.1. In this chapter, we look at all the POSIX.1 terminal functions and some of the platform-specific additions.

Part of the complexity of the terminal I/O system occurs because people use terminal I/O for so many different things: terminals, hardwired lines between computers, modems, printers, and so on.