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pty(7)                                                     pty(7)



NAME
     pty - provides a pseudo terminal driver

DESCRIPTION
     pty is a driver that  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  processes an interface identical to
     that described in termio(7).   However,  whereas  all  other
     devices  which  provide the interface described in termio(7)
     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 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 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 as with
               (CONTROL-S).

          TIOCPKT_START
               whenever output to the terminal is restarted.

          TIOCPKT_DOSTOP
               whenever t_stopc  is  CONTROL-S  and  t_startc  is
               CONTROL-Q.

          TIOCPKT_NOSTOP
               whenever the start and  stop  characters  are  not



January 1992                                                    1

pty(7)                                                     pty(7)



               CONTROL-S/CONTROL-Q.

          This mode is used  by  rlogin(1N)  and  rlogind(1M)  to
          implement  a remote-echoed, locally CONTROL-S/CONTROL-Q
          flow-controlled remote login with proper  back-flushing
          of output; it can be used by other similar programs.

LIMITATIONS
     It is not possible to send an EOT.

FILES
     /dev/pty[p-r][0-9a-f]
          Device files
     /dev/tty[p-r][0-9a-f]
          Device files








































2                                                    January 1992