freebsd man page for pts

PTS(4)							   BSD Kernel Interfaces Manual 						    PTS(4)

NAME
     pts -- pseudo-terminal driver

DESCRIPTION
     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 termi-
		   nal 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).

FILES
     The files used by this pseudo-terminals implementation are:

     /dev/pts/[num]  Pseudo-terminal slave devices.

DIAGNOSTICS
     None.

SEE ALSO
     posix_openpt(2), grantpt(3), ptsname(3), pty(4), tty(4)

HISTORY
     A pseudo-terminal driver appeared in 4.2BSD.  In FreeBSD 8.0, it was replaced with the pts driver.

BSD
								  August 20, 2008							       BSD