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pty - BSD-style compatibility pseudo-terminal driver
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
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.
The BSD-style compatibility pseudo-terminal driver uses the following
/dev/pty[l-sL-S][0-9a-v] Pseudo-terminal master devices.
/dev/tty[l-sL-S][0-9a-v] Pseudo-terminal slave devices.
posix_openpt(2), pts(4), tty(4)
A pseudo-terminal driver appeared in 4.2BSD.
Unlike previous implementations, the master 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
The pty driver cannot be unloaded, because it cannot determine if it is