NAME

ioctl, stty, gtty − control device

SYNOPSIS

#include <sgtty.h>

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

stty(fildes, argp)
struct sgttyb \(**argp;

gtty(fildes, argp)
struct sgttyb \(**argp;

DESCRIPTION

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

ioctl(fildes, TIOCSETP, argp)
ioctl(fildes, TIOCGETP, argp)

respectively; see tty(4).

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

ioctl(fildes, FIOCLEX, NULL);
ioctl(fildes, FIONCLEX, NULL);

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:

ioctl(fildes, FIONREAD, &count)

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

SEE ALSO

stty(1), tty(4), exec(2)

DIAGNOSTICS

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 ioctls 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))

BUGS

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’. 

ASSEMBLER (PDP-11)

(ioctl = 54.) 
sys ioctl; fildes; request; argp

(stty = 31.) 
(file descriptor in r0)
stty; argp

(gtty = 32.) 
(file descriptor in r0)
sys gtty; argp

th Berkeley Distribution