pts —
pseudo-terminal driver
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).
The files used by this pseudo-terminals implementation are:
- /dev/pts/[num]
- Pseudo-terminal slave devices.
None.
posix_openpt(2),
grantpt(3),
ptsname(3),
pty(4),
tty(4)
A pseudo-terminal driver appeared in
4.2BSD. In
FreeBSD 8.0, it was replaced with the
pts driver.