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 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 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.

Debian                                           August 20, 2008                                          PTS(4)