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98 lines
3.1 KiB
Groff
98 lines
3.1 KiB
Groff
.\" Copyright (c) 2008 Ed Schouten <ed@FreeBSD.org>
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.\" All rights reserved.
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.\"
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.\" Portions of this software were developed under sponsorship from Snow
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.\" B.V., the Netherlands.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd August 20, 2008
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.Dt PTY 4
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.Os
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.Sh NAME
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.Nm pty
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.Nd BSD-style and System V-style compatibility pseudo-terminal driver
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.Sh SYNOPSIS
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.Cd "device pty"
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.Sh DESCRIPTION
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The
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.Nm
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driver provides support for the traditional BSD naming scheme that was
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used for accessing pseudo-terminals.
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When the device
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.Pa /dev/ptyXX
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is being opened, a new terminal shall be created with the
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.Xr pts 4
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driver.
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A device node for this terminal shall be created, which has the name
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.Pa /dev/ttyXX .
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.Pp
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The
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.Nm
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driver also provides a cloning System V
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.Pa /dev/ptmx
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device.
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.Pp
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New code should not try to allocate pseudo-terminals using this
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interface.
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It is only provided for compatibility with older C libraries
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that tried to open such devices when
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.Xr posix_openpt 2
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was being called.
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.Sh FILES
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The BSD-style compatibility pseudo-terminal driver uses the following
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device names:
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.Bl -tag -width ".Pa /dev/pty[l-sL-S][0-9a-v]"
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.It Pa /dev/pty[l-sL-S][0-9a-v]
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Pseudo-terminal master devices.
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.It Pa /dev/tty[l-sL-S][0-9a-v]
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Pseudo-terminal slave devices.
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.It Pa /dev/ptmx
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Control device, returns a file descriptor to a new master
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pseudo-terminal when opened.
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.El
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.Sh DIAGNOSTICS
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None.
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.Sh SEE ALSO
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.Xr posix_openpt 2 ,
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.Xr pts 4 ,
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.Xr tty 4
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.Sh HISTORY
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A
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pseudo-terminal driver appeared in
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.Bx 4.2 .
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.Sh BUGS
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Unlike previous implementations, the master and slave device nodes are
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destroyed when the PTY becomes unused.
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A call to
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.Xr stat 2
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on a nonexistent master device will already cause a new master device
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node to be created.
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The master device can only be destroyed by opening and closing it.
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.Pp
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The
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.Nm
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driver cannot be unloaded, because it cannot determine if it is being
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used.
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