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IOCTL(2)		   Linux 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
       special files.  In particular, many operating characteristics of	 char-
       acter  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  ar-
       gument  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 pa-
       rameter 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 ioctl() requests  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.

ERRORS
       EBADF  d	is not a valid descriptor.

       EFAULT argp references an inaccessible memory area.

       EINVAL request or argp is not valid.

       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.

CONFORMING TO
       No  single standard.  Arguments,	returns, and semantics of ioctl() 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.

NOTES
       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.

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

COLOPHON
       This  page  is  part of release 3.74 of the Linux man-pages project.  A
       description of the project, information about reporting bugs,  and  the
       latest	  version     of     this    page,    can    be	   found    at
       http://www.kernel.org/doc/man-pages/.

Linux				  2013-11-08			      IOCTL(2)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | CONFORMING TO | NOTES | SEE ALSO | COLOPHON

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