IOCTL(2)						      BSD System Calls Manual							  IOCTL(2)

NAME

     ioctl -- control device

SYNOPSIS

     #include <sys/ioctl.h>

     int
     ioctl(int d, unsigned long request, char *argp);

DESCRIPTION

     The ioctl() function manipulates the underlying device parameters of special files.  In particular, many operating characteristics of charac-
     ter special files (e.g. terminals) may be controlled with ioctl() requests.  The argument d must be an open file descriptor.

     An  ioctl request has encoded in it whether the argument is an ``in'' parameter or ``out'' parameter, and the size of the argument argp in
     bytes.  Macros and defines used in specifying an ioctl request are located in the file <sys/ioctl.h>.

RETURN VALUES

     If an error has occurred, a value of -1 is returned and errno is set to indicate the error.

ERRORS

     Ioctl() will fail if:

     [EBADF]		d is not a valid descriptor.

     [ENOTTY]		d is not associated with a character special device.

     [ENOTTY]		The specified request does not apply to the kind of object that the descriptor d references.

     [EINVAL]		Request or argp is not valid.

SEE ALSO

     mt(1), cdio(1), chio(1), execve(2), fcntl(2), tty(4), intro(4)

HISTORY

     An ioctl() function call appeared in Version 7 AT&T UNIX.

4th Berkeley Distribution					 December 11, 1993					 4th Berkeley Distribution