ioctl - phpMan

IOCTL(2)                   Linux Programmer’s Manual                  IOCTL(2)



NAME
       ioctl - control device

SYNOPSIS
       #include <sys/ioctl.h>

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

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

       The second argument is a device-dependent request code.  The third argument  is  an
       untyped  pointer  to  memory.   It’s traditionally char *argp (from the days before
       void * was valid C), and will be so named for this discussion.

       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 VALUE
       Usually, on success zero is returned.  A few ioctls use the return value as an out-
       put parameter and return a nonnegative value on success.  On error, -1 is returned,
       and errno is set appropriately.

ERRORS
       EBADF  d is not a valid descriptor.

       EFAULT argp references an inaccessible memory area.

       ENOTTY d is not associated with a character special device.

       ENOTTY The specified request does not apply to the kind of object that the descrip-
              tor d references.

       EINVAL Request or argp is not valid.

NOTE
       In  order  to  use this call, one needs an open file descriptor.  Often the open(2)
       call has unwanted side effects, that can be avoided under Linux by  giving  it  the
       O_NONBLOCK flag.

CONFORMING TO
       No  single  standard.  Arguments, returns, and semantics of ioctl(2) vary according
       to the device driver in question (the call is used as a  catch-all  for  operations
       that  don’t cleanly fit the Unix stream I/O model). See ioctl_list(2) for a list of
       many of the known ioctl calls.  The ioctl function call appeared in Version 7  AT&T
       Unix.

SEE ALSO
       execve(2), fcntl(2), ioctl_list(2), open(2), mt(4), sd(4), tty(4)



BSD Man Page                      2000-09-21                          IOCTL(2)

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