A/UX® System Administrator's Reference Sections 1M, 7, and 8

termio(7) termio(7)
NAME
termio - general terminal interface
DESCRIPTION
This section describes both a particular file and the terminal interface.
The file / dev / tty is, in each process, the control terminal associated
with the process group of that process. Programs or shell
sequences use it to ensure that their messages appear on the terminal,
no matter how output is redirected. Also, programs that
demand an output filename will accept / dev / tty, so the terminal
being used is unimportant.
The asynchronous communications ports use the same general interface,
no matter what their hardware. This section discusses the
common features of this interface.
When a terminal file is opened, it normally makes the process wait
until it establishes a connection. Users' programs seldom open
these files; getty(IM) opens them and they become a user's
standard input, output, and error files. The first terminal file the
process-group leader opens, which is not already associated with a
process group, becomes the control terminal for that process
group. The control terminal plays a special role in handling quit
and interrupt signals, as discussed later. The control terminal is
inherited by a child process during a fork(2). A process breaks
this association by changing its process group (using
setpgrp(2)).
Tenninals associated with one of these files operate in full-duplex
mode. You may type at any time, even while the terminal is printing.
Characters you type are lost only when the system's character
input buffers are full, which is rare, or when you have accumulated
the maximum number of input characters that have not been
read by some program. Currently, this limit is 256 characters.
When you reach the input limit, all the saved characters are
thrown away without notice.
Normally, tenninal input is processed in units of lines. A line is
delimited by a newline (ASCII LF) character, an end-of-file
(ASCII EOn character, or an end-of-line character. This means
that a program cannot read input until you have typed an entire
line. Also, no matter how many characters a read(2) system call
requests, a maximum of one line is returned. It is not, however,
necessary to read a whole line at once; a read can request any
February, 1990
Revision C
1