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     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

                   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.




     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