.\" Copyright (c) 2001
.\"	The FreeBSD Project
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.\" $FreeBSD: src/share/man/man4/nmdm.4,v 1.2.2.1 2001/08/11 00:54:14 mp Exp $
.\" $DragonFly: src/share/man/man4/nmdm.4,v 1.2 2003/06/17 04:36:59 dillon Exp $
.\"
.Dd July 7, 2001
.Dt NMDM 4
.Os
.Sh NAME
.Nm nmdm
.Nd nullmodem terminal driver
.Sh SYNOPSIS
.Cd "device nmdm"
.Sh DESCRIPTION
The
.Nm
driver provides support for a device-pair termed a
.Em null modem pair .
A null modem pair is a pair of character devices.
Each device provides to a process an interface identical
to that described in
.Xr tty 4 .
However, whereas most other devices which provide the
interface described in
.Xr tty 4
have a hardware device of some sort behind them, the
.Nm
device has, instead, another process manipulating
it through the other half of the pair.
That is, anything written on the first device is
given to the second device as input and anything written
on the second device is presented as input on the first
device.
.Sh FILES
.Bl -tag -width /dev/nmdm[N][AB] -compact
.It Pa /dev/nmdm Ns Ar N Ns Op Pa AB
nullmodem device nodes.
Where the
.Pa A
node has a matching
.Pa B
node.
.El
.Sh DIAGNOSTICS
None.
.Sh SEE ALSO
.Xr tty 4
.Sh HISTORY
The
.Nm
driver first appeared in
.Fx 4.4 .