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 file 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 file 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 filesystem, 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 4.15 of the Linux man-pages project.  A description of the project, information about reporting bugs, and the
       latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.

Linux								    2016-03-15								    PTS(4)