1.\" Copyright (c) 2001 2.\" The FreeBSD Project 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 10.\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND 11.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 12.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 13.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE 14.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 15.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 16.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 17.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 18.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 19.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 20.\" SUCH DAMAGE. 21.\" 22.\" $FreeBSD$ 23.\" 24.Dd July 7, 2001 25.Dt NMDM 4 26.Os 27.Sh NAME 28.Nm nmdm 29.Nd nullmodem terminal driver 30.Sh SYNOPSIS 31.Cd "device nmdm" 32.Sh DESCRIPTION 33The 34.Nm 35driver provides support for a device-pair termed a 36.Em null modem pair . 37A null modem pair is a pair of character devices. 38Each device provides to a process an interface identical 39to that described in 40.Xr tty 4 . 41However, whereas most other devices which provide the 42interface described in 43.Xr tty 4 44have a hardware device of some sort behind them, the 45.Nm 46device has, instead, another process manipulating 47it through the other half of the pair. 48That is, anything written on the first device is 49given to the second device as input and anything written 50on the second device is presented as input on the first 51device. 52.Sh FILES 53.Bl -tag -width /dev/nmdm[N][AB] -compact 54.It Pa /dev/nmdm Ns Ar N Ns Op Pa AB 55nullmodem device nodes. 56Where the 57.Pa A 58node has a matching 59.Pa B 60node. 61.El 62.Sh DIAGNOSTICS 63None. 64.Sh SEE ALSO 65.Xr tty 4 66.Sh HISTORY 67The 68.Nm 69driver first appeared in 70.Fx 4.4 . 71