Copyright (c) 1980 Regents of the University of California.
All rights reserved. The Berkeley software License Agreement
specifies the terms and conditions for redistribution.

@(#)ioctl.2 4.1 (Berkeley) 05/09/85

C 4 ioctl, stty, gtty - control device

 #include <sgtty.h> 

 ioctl(fildes, request, argp)  struct sgttyb *argp; 

 stty(fildes, argp)  struct sgttyb *argp; 

 gtty(fildes, argp)  struct sgttyb *argp; 

Ioctl performs a variety of functions on character special files (devices). The writeups of various devices in section 4 discuss how ioctl applies to them.

For certain status setting and status inquiries about terminal devices, the functions stty and gtty are equivalent to

respectively; see tty (4).

The following two standard calls, however, apply to any open file:

The first causes the file to be closed automatically during a successful exec operation; the second reverses the effect of the first.

The following call is peculiar to the Berkeley implementation, and also applies to any open file:

returning, in the longword count the number of characters available for reading from fildes.

stty(1), tty(4), exec(2) Zero is returned if the call was successful; -1 if the file descriptor does not refer to the kind of file for which it was intended, or if request attempts to modify the state of a terminal when fildes is not writeable.

Ioctl calls which attempt to modify the state of a process control terminal while a process is not in the process group of the control terminal will cause a SIGTTOU signal to be sent to the process' process group. Such ioctl s are allowed, however, if SIGTTOU is being held, ignored, if the process is an orphan which has been inherited by init , or is the child in an incomplete vfork (see jobs (3))

Strictly speaking, since ioctl may be extended in different ways to devices with different properties, argp should have an open-ended declaration like union { struct sgttyb ... ; ... } *argp;

The important thing is that the size is fixed by `struct sgttyb'.

(ioctl = 54.)

sys ioctl; fildes; request; argp

(stty = 31.)

(file descriptor in r0)

stty; argp

(gtty = 32.)

(file descriptor in r0)

sys gtty; argp