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nmdm(4) [freebsd man page]

NMDM(4) 						   BSD Kernel Interfaces Manual 						   NMDM(4)

NAME
nmdm -- nullmodem terminal driver SYNOPSIS
device nmdm DESCRIPTION
The nmdm driver provides two tty(4) devices connected by a virtual ``null modem'' cable. If either of the two tty devices have the CDSR_OFLOW bit (``stty dsrflow'') set in their line discipline, the nmdm device will emulate the speed configured in the termios(4) settings. The speed emulation works independently in the two directions, controlled by the slower end's termios settings (c_ispeed, c_ospeed, CS5 ... CS8, CSTOPB and PARENB). FILES
/dev/nmdmN[AB] nullmodem device nodes. Where the A node has a matching B node. The nmdm driver implements ``on-demand device creation'' so simply accessing a given instance in /dev will create it. DIAGNOSTICS
None. SEE ALSO
stty(1), termios(4), tty(4) HISTORY
The nmdm driver first appeared in FreeBSD 4.4. BSD
January 27, 2005 BSD

Check Out this Related Man Page

PTY(4)							   BSD Kernel Interfaces Manual 						    PTY(4)

NAME
pty -- BSD-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. 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. 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 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. BSD
August 20, 2008 BSD

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