bionic (4) pty.4freebsd.gz

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NAME
     pty — BSD-style and System V-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.  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.


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.