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NAME

     ioctl - control device

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <sys/ioctl.h>

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

DESCRIPTION

     The ioctl() system call manipulates the underlying device parameters of
     special 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 to ioctl() is traditionally named char *argp.  Most
     uses of ioctl(), however, require the third argument to be a caddr_t or
     an int.

     An ioctl() request has encoded in it whether the argument is an “in”
     argument or “out” argument, and the size of the argument argp in bytes.
     Macros and defines used in specifying an ioctl request are located in the
     file

RETURN VALUES

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

ERRORS

     The ioctl() system call will fail if:

     [EBADF]            The d argument is not a valid descriptor.

     [ENOTTY]           The d argument 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]           The request or argp argument is not valid.

     [EFAULT]           The argp argument points outside the process’s
                        allocated address space.

SEE ALSO

     execve(2), fcntl(2), intro(4), tty(4)

HISTORY

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