PTS(4)                    (2020-08-13)                     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 associated 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 written to the master is pre-
          sented to the slave as input.

          In practice, pseudoterminals are used for implementing ter-
          minal emulators such as xterm(1), in which data read from
          the pseudoterminal master 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 pseudoter-
          minal naming) is done using the devpts filesystem, which
          should be mounted on /dev/pts.

     SEE ALSO

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     PTS(4)                    (2020-08-13)                     PTS(4)

          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/.

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