pty —
old-style
compatibility pseudo-terminal driver
device pty
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.
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.
None.
posix_openpt(2),
pts(4),
tty(4)
A pseudo-terminal driver appeared in
4.2BSD.
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.