hpux man page for ioctl

ioctl(5)							File Formats Manual							  ioctl(5)

NAME
       ioctl - generic device control commands

SYNOPSIS
DESCRIPTION
       The ioctl(2) system call provides for control over open devices.  This include file describes requests and arguments used in ioctl(2) which
       are of a generic nature.  For details about how individual requests will affect any particular device, see the corresponding device  manual
       entry in Section 7 of the If a device does not support an ioctl request it returns

       Returns in the long integer whose address is
			   arg the number of characters immediately readable from the device file.

       For those character device files which support this command,
			   if  the  integer whose address is arg is nonzero, system asynchronous I/O is enabled; that is, enable to be sent to the
			   process currently designated with (see below) whenever device-file-dependent events occur.  If no process has been des-
			   ignated with then enable to be sent to the first process to open the device file.

			   If the designated process has exited, the signal is not sent to any process.

			   If the integer whose address is arg is 0, system asynchronous I/O is disabled.

       For those character device files which support this command,
			   the	integer  whose	address  is  arg is set to 1, if system asynchronous I/O is enabled.  Otherwise, the integer whose
			   address is arg is set to 0.

       For those character device files which support this command,
			   set process ID to receive the signals with system asynchronous I/O to the value of the integer whose  address  is  arg.
			   Users  with	appropriate  privileges can designate that any process receive the signals.  If the request is not made by
			   the super-user, only the calling process is allowed to designate that itself or another process  whose  real  or  saved
			   effective  user  ID	matches  its real or effective user ID, or a process which is a descendant of the calling process,
			   receive the signals.  If no process can be found corresponding to that specified by the integer whose address  is  arg,
			   the call will fail, with set to If the request is not made by the super-user and the calling process attempts to desig-
			   nate a process other than itself or (1) another process whose real or saved effective  user	ID  matches  its  real	or
			   effective user ID, or (2) a process which is not a descendant of the calling process, the call fails, with set to

			   If the designated process subsequently exits, the signal will not be sent to any process.

			   The default when opening a device file is that the process performing the open is set to receive the signals.

       For those character device files which support this command,
			   the integer whose address is arg is set to the process ID designated to receive signals.

       For those character device files which support this command,
			   if the integer whose address is arg is nonzero, nonblocking I/O is enabled; that is, subsequent reads and writes to the
			   device file are handled in a nonblocking manner (see below).  If the integer whose address is arg is 0, nonblocking I/O
			   is disabled.

			   For	reads,	nonblocking  I/O  prevents all read requests to that device from blocking, whether the requests succeed or
			   fail.  Such read requests complete in one of three ways:

			 o  If there is enough data available to satisfy the entire request, the read completes successfully, having read  all	of
			    the data, and returns the number of bytes read;

			 o  If	there  is not enough data available to satisfy the entire request, the read completes successfully, having read as
			    much data as possible, and returns the number of bytes it was able to read;

			 o  If there is no data available, the read fails and errno is set to

			   For writes, nonblocking I/O prevents all write requests to that device file from blocking, whether the requests succeed
			   or fail.  Such a write request completes in one of three ways:

			 o  If	there  is  enough  space  available in the system to buffer all the data, the write completes successfully, having
			    written out all of the data, and returns the number of bytes written;

			 o  If there is not enough space in the buffer to write out the entire request, the write completes  successfully,  having
			    written as much data as possible, and returns the number of bytes it was able to write;

			 o  If there is no space in the buffer, the write fails and is set to

			   To  prohibit  nonblocking  I/O  from  interfering with the flag (see open(2) and fcntl(2)), the functionality of always
			   supersedes the functionality of nonblocking I/O.  This means that if is set,  the  driver  performs	read  requests	in
			   accordance with the definition of When is not set, the definition of nonblocking I/O applies.

			   The default on open of a device file is that nonblocking I/O is disabled.

       For those character device files which support this command,
			   the	integer  whose address is arg is set to 1, if nonblocking I/O is enabled.  Otherwise, the integer whose address is
			   arg is set to 0.

WARNINGS
       is similar to 4.2 BSD with the addition of provisions for security.

       is of HP origin, complements and allows saving and restoring system asynchronous I/O TTY state for BSD-style job control.

       is similar to 4.2 BSD with the addition of provisions for security.

       is similar to 4.2 BSD Note also the difference that the 4.2 BSD version of this functionality used process groups, while the HP-UX  version
       only uses processes.

       is the same as 4.2 BSD except that it does not interfere with the AT&T open and fcntl flag.

       is of HP origin, complements and allows saving and restoring nonblocking I/O TTY state for BSD-style job control.

SEE ALSO
       ioctl(2), arp(7), socket(7).

       Section 7 of the

																	  ioctl(5)