PTY(4)                 FreeBSD Kernel Interfaces Manual                 PTY(4)

NAME
     pty - old-style compatibility pseudo-terminal driver

SYNOPSIS
     device pty

DESCRIPTION
     The pty driver provides support for the traditional BSD naming scheme
     that was used for accessing pseudo-terminals before it was replaced by
     pts(4).  This traditional naming is still used in Linux.  When the device
     /dev/ptyXX is being opened, a new terminal shall be created with the
     pts(4) driver.  A device node for this terminal shall be created, which
     has the name /dev/ttyXX.

     The pty driver also provides a cloning System V /dev/ptmx device.

     New code should not try to allocate pseudo-terminals using this
     interface.  It is only provided for compatibility with older C libraries
     that tried to open such devices when posix_openpt(2) was being called,
     and for running Linux binaries.

FILES
     The BSD-style compatibility pseudo-terminal driver uses the following
     device names:

     /dev/pty[l-sL-S][0-9a-v]      Pseudo-terminal master devices.

     /dev/tty[l-sL-S][0-9a-v]      Pseudo-terminal slave devices.

     /dev/ptmx                     Control device, returns a file descriptor
                                   to a new master pseudo-terminal when
                                   opened.

DIAGNOSTICS
     None.

SEE ALSO
     posix_openpt(2), pts(4), tty(4)

HISTORY
     A pseudo-terminal driver appeared in 4.2BSD.

BUGS
     Unlike previous implementations, the master and slave device nodes are
     destroyed when the PTY becomes unused.  A call to stat(2) on a
     nonexistent master device will already cause a new master device node to
     be created.  The master device can only be destroyed by opening and
     closing it.

     The pty driver cannot be unloaded, because it cannot determine if it is
     being used.

FreeBSD 13.1-RELEASE-p6        October 28, 2019        FreeBSD 13.1-RELEASE-p6