


      PTY(7)                      (bsd 4.2)                      PTY(7)



      NAME
           pty - pseudo terminal driver

      DESCRIPTION
           The pty 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 an interface identical to that described in
           termio(7).  Typically, devices that provide the interface
           described in termio(7) have a hardware device of some sort
           behind them.  Instead, the slave device has 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 calls apply only to pseudo terminals:

           TIOCSTOP
                Stops output to a terminal (e.g. like typing ^S).
                Takes no parameter.

           TIOCSTART
                Restarts output (stopped by TIOCSTOP or by typing ^S).
                Takes no parameter.

           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 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.



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      PTY(7)                      (bsd 4.2)                      PTY(7)



                TIOCPKT_DOSTOP
                     whenever t_stopc is ^S and t_startc is ^Q.

                TIOCPKT_NOSTOP
                     whenever the start and stop characters are not
                     ^S/^Q.

                This mode is used by rlogin(1) and rlogind(1) 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.

           TIOCREMOTE
                A mode for the master half of a pseudo terminal,
                independent of TIOCPKT.  This mode causes input to the
                pseudo terminal to be flow controlled and not input
                edited (regardless of the 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 an end-of-
                file character.  TIOCREMOTE can be used when doing
                remote line editing in a window manager, or whenever
                flow controlled input is required.

                The pseudo terminal driver is actually implemented by
                the tty driver (either /drivers/fdlp for systems with a
                FDLP controller, or /drivers/ciotty for systems with a
                CIO controller and /drivers/asyn for systems with a SAS
                controller).  The major device numbers to be used for
                pseudo terminals depends on which driver is being used.
                The maximum number of pseudo terminals per system is
                16, and they must be named in order from 0 to 9, a to
                f.  The maximum number of pseudo terminals per driver
                depends on the driver: 4 for fdlp, 8 for ciotty and
                asyn.


      DEVICE CODE
           For FDLP:
                                         block-type or  standard
           device type              major     minor     character-type file name

           slave pseudo terminal         10   0..15     char      /dev/ttyp0..ttypf
           master pseudo terminal        11   0..15     char      /dev/ptyp0..ptypf

           For CIO:
                                         block-type or  standard
           device type              major     minor     character-type file name

           slave pseudo terminal         16   0..15     char      /dev/ttyp0..ttypf
           master pseudo terminal        17   0..15     char      /dev/ptyp0..ptypf



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      PTY(7)                      (bsd 4.2)                      PTY(7)



           For SAS:
                                         block-type or  standard
           device type              major     minor     character-type file name

           slave pseudo terminal         134  0..15     char      /dev/ttyp0..ttypf
           master pseudo terminal        135  0..15     char      /dev/ptyp0..ptypf


      FILES
           /dev/ptyp[0-f] master (control) pseudo terminals
           /dev/ttyp[0-f] slave pseudo terminals
           /drivers/fdlp, /drivers/ciotty, /drivers/asyn











































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