IOCTL(2)                COMMAND REFERENCE                IOCTL(2)



NAME
     ioctl - control device

SYNOPSIS
     #include <sys/ioctl.h>

     ioctl(fd, request, argp)
     int fd;
     long request;
     char *argp;

DESCRIPTION
     Ioctl performs a variety of functions, specified by request,
     on the open descriptor fd. In particular, many operating
     characteristics of character special files (e.g. terminals)
     may be controlled with ioctl requests.

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

     The writeups of various devices in section 4 discuss how
     ioctl applies to them.  See that section for details.

DIAGNOSTICS
     Ioctl will fail if one or more of the following are true:

     [EBADF]      Fd is not a valid open descriptor, or the
                  object it references is not readable or
                  writable.

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

     [EINVAL]     Request or argp is not valid.

     [EFAULT]     Argp references an invalid address.

     [EFAULT]     The size encoded in request is invalid.

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

SEE ALSO
     execve(2), fcntl(2), tty(4), and intro(4n).







Printed 4/6/89                                                  1

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