IOCTL(2)                  OpenBSD Programmer's Manual                 IOCTL(2)

NAME
     ioctl - control device



SYNOPSIS
     #include <sys/ioctl.h>

     int
     ioctl(int d, unsigned long request, ...);

DESCRIPTION
     The ioctl() function manipulates the underlying device parameters of spe-
     cial files.  In particular, many operating characteristics of character
     special files (e.g. terminals) may be controlled with ioctl() requests.

     The argument d must be an open file descriptor. The third argument is
     called arg and contains additional information needed by this device to
     perform the requested function.  arg is either an int or a pointer to a
     device-specific data structure, depending upon the given request.

     An ioctl request has encoded in it whether the argument is an ``in'' pa-
     rameter or ``out'' parameter, and the size of the third argument (arg) in
     bytes.  Macros and defines used in specifying an ioctl request are locat-
     ed 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
     cdio(1),  chio(1),  mt(1),  execve(2),  fcntl(2),  intro(4),  tty(4)

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

OpenBSD 2.6                    December 11, 1993                             1