ptmx(4) - phpMan

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

NAME
       ptmx, pts - pseudoterminal master and slave

DESCRIPTION
       The  file /dev/ptmx (the pseudoterminal multiplexor device) is a character file with major
       number 5 and minor number 2, usually with mode 0666 and ownership 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 and
       a pseudoterminal slave device is created in the /dev/pts directory.  Each file  descriptor
       obtained by opening /dev/ptmx is an independent pseudoterminal master with its own associ-
       ated slave, 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 writ-
       ten 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 master is interpreted by the applica-
       tion  in  the  same way a real terminal would interpret the data, and for implementing re-
       mote-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, which should be mounted on /dev/pts.

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

COLOPHON
       This page is part of release 5.10 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                                       2020-08-13                                     PTS(4)

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