pty man page on BSDOS

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PTY(4)			    BSD Programmer's Manual			PTY(4)

NAME
     pty - pseudo terminal driver

SYNOPSIS
     pseudo-device pty [count]

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 de-
     vice and a slave device.  The slave device provides to a process an in-
     terface identical to that described in tty(4).  However, whereas all oth-
     er devices which provide the interface described in tty(4) have a hard-
     ware device of some sort behind them, the slave device has, instead, an-
     other process manipulating it through the master half of the pseudo ter-
     minal.  That is, anything written on the master device is given to the
     slave device as input and anything written on the slave device is pre-
     sented as input on the master device.

     In configuring, if an optional count is given in the specification, that
     number of pseudo terminal pairs are configured; the default count is 32.

     The following ioctl(2) 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.  TIOCSIG Sends the specified signal to
		 the process group members of the pseudo terminal that have it
		 as their controlling terminal.

     TIOCPKT	 Enable/disable packet mode.  Packet mode is enabled by speci-
		 fying (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 in-
		 clusive-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 in-
		 formation 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.

     TIOCUCNTL	 Enable/disable a mode that allows a small number of simple
		 user ioctl commands to be passed through the pseudo-terminal,
		 using a protocol similar to that of TIOCPKT. The TIOCUCNTL
		 and TIOCPKT modes are mutually exclusive.  This mode is en-
		 abled from the master side of a pseudo terminal by specifying
		 (by reference) a nonzero parameter and disabled by specifying
		 (by reference) a zero parameter.  Each subsequent read from
		 the master side will return data written on the slave part of
		 the pseudo terminal preceded by a zero byte, or a single byte
		 reflecting a user control operation on the slave side.	 A us-
		 er control command consists of a special ioctl operation with
		 no data; the command is given as UIOCCMD(n), where n is a
		 number in the range 1-255.  The operation value n will be re-
		 ceived as a single byte on the next read from the master
		 side.	The ioctl UIOCCMD(0) is a no-op that may be used to
		 probe for the existence of this facility.  As with TIOCPKT
		 mode, command operations may be detected with a select for
		 exceptional conditions.

     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 re-
		 mote line editing in a window manager, or whenever flow con-
		 trolled input is required.

FILES
     /dev/pty[p-r][0-9a-f]   master pseudo terminals
     /dev/tty[p-r][0-9a-f]   slave pseudo terminals

DIAGNOSTICS
     None.

HISTORY
     The pty driver appeared in 4.2BSD.

4.2 Berkeley Distribution      December 8, 1994				     2
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