The
pts
driver provides support for a device-pair termed a
pseudo-terminal.
A pseudo-terminal is a pair of character devices, a
master
device and a
slave
device.
The slave device provides to a process an interface identical
to that described in
tty(4).
However, whereas all other devices which provide the
interface described in
tty(4)
have a hardware device of some sort behind them, the slave
device has, instead, another process manipulating
it through the master half of the pseudo-terminal.
That is, anything written on the master device is
given to the slave device as input and anything written
on the slave device is presented as input on the master
device.
The following
ioctl(2)
calls apply only to pseudo-terminals:
|
| TIOCPKT
|
Enable/disable
packet
mode.
Packet mode is enabled by specifying (by reference)
a nonzero parameter and disabled by specifying (by reference)
a zero parameter.
When applied to the master side of a pseudo-terminal, each subsequent
read(2)
from the terminal will return data written on the slave part of
the pseudo-terminal preceded by a zero byte (symbolically
defined as
TIOCPKT_DATA),
or a single byte reflecting control
status information.
In the latter case, the byte is an inclusive-or
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 a la
‘^S’.
|
| TIOCPKT_START
|
whenever output to the terminal is restarted.
|
| TIOCPKT_DOSTOP
|
whenever
VSTOP
is
‘^S’
and
VSTART
is
‘^Q’.
|
| TIOCPKT_NOSTOP
|
whenever the start and stop characters are not
‘^S/^Q’.
|
|
While this mode is in use, the presence of control status information
to be read from the master side may be detected by a
select(2)
for exceptional conditions.
This mode is used by
rlogin(1)
and
rlogind(8)
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.
| TIOCGPTN
|
Obtain device unit number, which can be used to generate the filename of
the pseudo-terminal slave device.
This
ioctl(2)
should not be used directly.
Instead, the
ptsname(3)
function should be used.
|
| TIOCPTMASTER
|
Determine whether the file descriptor is pointing to a pseudo-terminal
master device.
This
ioctl(2)
should not be used directly.
It is used to implement routines like
grantpt(3).
|
|
