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

       ioctl - control device

       #include <sys/ioctl.h>

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

       The ioctl function manipulates the underlying device parameters of special files.  In par-
       ticular, 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  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 parame-
       ter, 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>.

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

       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 descriptor d

       EINVAL Request or argp is not valid.

       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.

       execve(2), fcntl(2), ioctl_list(2), mt(4), sd(4), tty(4)

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