PTS(4)							     Linux Programmer's Manual							    PTS(4)

NAME

       ptmx, pts - pseudoterminal master and slave

DESCRIPTION

       The  file  /dev/ptmx  is a character file with major number 5 and minor number 2, usually of mode 0666 and owner.group of root.root.  It is
       used to create a pseudoterminal master and slave pair.

       When a process opens /dev/ptmx, it gets a file descriptor for a pseudoterminal master (PTM), and a pseudoterminal  slave  (PTS)	device	is
       created	in  the /dev/pts directory.  Each file descriptor obtained by opening /dev/ptmx is an independent PTM with its own associated PTS,
       whose path can be found by passing the descriptor to ptsname(3).

       Before opening the pseudoterminal slave, you must pass the master's file descriptor to grantpt(3) and unlockpt(3).

       Once both the pseudoterminal master and slave are open, the slave provides processes with an interface that is identical to that of a  real
       terminal.

       Data written to the slave is presented on the master descriptor as input.  Data written to the master is presented to the slave as input.

       In practice, pseudoterminals are used for implementing terminal emulators such as xterm(1), in which data read from the pseudoterminal mas-
       ter is interpreted by the application in the same way a real terminal would interpret the data, and for implementing remote-login  programs
       such  as  sshd(8),  in which data read from the pseudoterminal master is sent across the network to a client program that is connected to a
       terminal or terminal emulator.

       Pseudoterminals can also be used to send input to programs that normally refuse to read input from pipes (such as su(1), and passwd(1)).

FILES

       /dev/ptmx, /dev/pts/*

NOTES

       The Linux support for the above (known as UNIX 98 pseudoterminal naming) is done using the devpts file system, that should  be  mounted	on
       /dev/pts.

       Before  this  UNIX 98 scheme, master pseudoterminals were called /dev/ptyp0, ...  and slave pseudoterminals /dev/ttyp0, ...  and one needed
       lots of preallocated device nodes.

SEE ALSO

       getpt(3), grantpt(3), ptsname(3), unlockpt(3), pty(7)

COLOPHON

       This page is part of release 3.44 of the Linux man-pages project.  A description of the project, and information about reporting bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

Linux								    2002-10-09								    PTS(4)