VTY(ADMP)                                  UNIX System V



     Name
          vty - pseudo terminal slave driver


     Name
          ttyp - pseudo terminal master driver


     Description
          The ttyp and vty drivers  together  provide  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(ADMP).   However,
          whereas  all  other  devices  which  provide  the  interface
          described in termio(ADMP) 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 call applies 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  a  la
                    ^S.

               TIOCPKT_START
                    whenever output to the terminal is restarted.

               TIOCPKT_DOSTOP
                    whenever t_stopc is ^S and t_startc 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 for exceptional conditions.


          This  mode  is  used  by  rlogin(TC)  and  rlogind(ADMN)  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.


     Files
          /dev/ptyp[0-f][0-f] master pseudo terminals
          /dev/ttyp[0-f][0-f] slave pseudo terminals


     See Also
          termio(ADMP).


     (printed 8/17/89)                                  VTY(ADMP)