.\"        $NetBSD: ptm.4,v 1.8 2013/12/01 00:17:14 christos Exp $
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.\" Copyright (c) 2004 Thomas Klausner
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.Dd November 30, 2013
.Dt PTM 4
.Os
.Sh NAME
.Nm ptm
.Nd pseudo-terminal multiplexor device
.Sh SYNOPSIS
.Cd pseudo-device pty
.Sh DESCRIPTION
The
.Nm
driver is the backend for the
.Pa /dev/ptm
device.
It supports three
.Xr ioctl 2 Ns s .
The first is
.Dv TIOCPTMGET ,
which allocates a free pseudo-terminal device, sets its user ID to
the calling user,
.Xr revoke 2 Ns s
it, and returns the opened file descriptors for both the master
and the slave pseudo-terminal device to the caller in a
.Va struct ptmget .
This struct has the following content:
.Bd -literal -offset indent
struct ptmget {
        int     cfd;
        int     sfd;
        char    cn[PATH_MAX];
        char    sn[PATH_MAX];
};
.Ed
.Pp
where
.Va cfd
and
.Va sfd
contain the master resp. slave device's file descriptor and
.Va cn
and
.Va sn
the corresponding paths in the file system.
.Pp
The
.Pa /dev/ptmx
device supports two more
.Xr ioctl 2 Ns s ,
.Dv TIOCGRANTPT ,
which is used by
.Xr grantpt 3 ,
.Dv TIOCPTSNAME ,
which is used by
.Xr ptsname 3 .
.Pp
The
.Nm
device is included with the pseudo-device
.Xr pty 4 .
It can be disabled by adding
.Dq Cd options NO_DEV_PTM
to the kernel configuration.
.Sh FILES
.Bl -tag
.It Pa /dev/ptm
.Nm
access device
.It Pa /dev/ptmx
.Nm
cloning device, used to implement Unix98 ptys
.El
.Sh SEE ALSO
.Xr grantpt 3 ,
.Xr openpty 3 ,
.Xr posix_openpt 3 ,
.Xr ptsname 3 ,
.Xr unlockpt 3 ,
.Xr pty 4
.Sh HISTORY
The
.Pa /dev/ptm
device appeared in
.Ox 3.5
and was ported to
.Nx 3.0 .