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.