.TH IOCTLNEW 2X 3/17/82
.UC 4.1a Provisional
.SH NAME
ioctlnew \- description of some new ioctls
.SH DESCRIPTION
.TP 5
FIONBIO
Takes an integer parameter saying whether non-blocking i/o is
desired on the specified file.
Applies to terminals, pipe, pseudo-terminals and sockets and
specifies that operations are to return EWOULDBLOCK rather than
blocking.  A
.IR select (2x)
operation may be used to determine when i/o is possible without
busy polling.
.TP 5
FIOASYNC
Takes an integer parameter saying whether interrupt notification
that i/o is possible using SIGIO is desired for the specified
descriptor.  (Not yet implemented.)
.PP
The following controls are useful in implementing remote terminal
facilities:
.TP 5
TIOCSTOP
Stops output to a terminal (e.g. like typing ^S).  Takes no parameter.
.TP 5
TIOCSTART
Restarts output (stopped by TIOCSTOP or by typing ^S).  Takes no parameter.
.TP 5
TIOCNOTTY
A mode enabled or disabled with an integer parameter.
When applied to /dev/tty for a process removes any terminal
and process group association for that process, returning
it to the class of process shown only by ``ps x''.
.TP 5
TIOCPKT
A mode enabled or disabled with a parameter (the address of a) 0 or 1.
When applied to the controlling terminal of a pseudo-terminal
(e.g. /dev/ptyp?) causes subsequent data to be read preceded by a zero
byte (symbolically defined as TIOCPKT_DATA.
The other possibility in packet mode is a single byte reflecting
control status information.  This byte is an inclusive of zero or
more of the bits:
TIOCPKT_FLUSHREAD whenever the read queue for the terminal is flushed,
TIOCPKT_FLUSHWRITE whenever the write queue for the terminal is flushed,
TIOCPKT_STOP whenever output to the terminal is stopped ala ^S,
TIOCPKT_START whenever output is restarted.
In addition, each control byte contains TIOCPKT_DOSTOP if the
start and stop characters on the terminal are currently ^S and ^Q,
and TIOCPKT_NOSTOP if they are not.
This mode is used by
.IR rlogin (1c)
to implement a remote-echoed, locally ^S/^Q flow controlled remote
login with proper back-flushing of output; it can be used by
other similar programs.
.TP 5
TIOCREMOTE
A mode for the control terminal of a pseudo-terminal, independent of TIOCPKT.
This mode causes input to the pty to be flow controlled and not input edited
(regardless of terminal mode).  Each write to the control terminal produces
a record boundary for the process reading the terminal.  In normal
usage, a write of data is like the data typed as a line on the terminal;
a write of 0 bytes is like typing ^D.  TIOCREMOTE can be used when
doing remote line editing in a window manager, or whenever flow controlled
input is required.
.SH SEE ALSO
socket(2x), ioctl(2)
.SH BUGS
FIONBIO actually applies to the underlying entity (e.g. the terminal)
rather than an instance (e.g. result of a single open).  This
is undoubtedly wrong and will be fixed.
.PP
These controls are provisional, and may exist in different forms
in 4.2bsd.  In particular, the modes for the controlling half of
pseudo-terminals are instances of kernel ``protocol support'' for
user-assisted implementation of system abstractions.
More support for this kind of system extensibility will be more provided
in 4.2.