00ee13a0af
When I wrote the pseudo-terminal driver for the MPSAFE TTY code, Robert Watson and I agreed the best way to implement this, would be to let posix_openpt() create a pseudo-terminal with proper permissions in place and let grantpt() and unlockpt() be no-ops. This isn't valid behaviour when looking at the spec. Because I thought it was an elegant solution, I filed a bug report at the Austin Group about this. In their last teleconference, they agreed on this subject. This means that future revisions of POSIX may allow grantpt() and unlockpt() to be no-ops if an open() on /dev/ptmx (if the implementation has such a device) and posix_openpt() already do the right thing. I'd rather put this in the manpage, because simply mentioning we don't comply to any standard makes it look worse than it is. Right now we don't, but at least we took care of it. Approved by: re (kib) MFC after: 3 days
161 lines
4.2 KiB
Groff
161 lines
4.2 KiB
Groff
.\"
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.\" Copyright (c) 2002 The FreeBSD Project, Inc.
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.\" All rights reserved.
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.\"
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.\" This software includes code contributed to the FreeBSD Project
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.\" by Ryan Younce of North Carolina State University.
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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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.\" 3. Neither the name of the FreeBSD Project nor the names of its
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.\" contributors may be used to endorse or promote products derived from
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.\" this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE FREEBSD PROJECT AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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.\" LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
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.\" PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FREEBSD PROJECT
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.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
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.\" TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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.\" LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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.\" NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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.\" SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 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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.Os
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.Dt PTSNAME 3
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.Sh NAME
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.Nm grantpt ,
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.Nm ptsname ,
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.Nm unlockpt
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.Nd pseudo-terminal access functions
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In stdlib.h
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.Ft int
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.Fn grantpt "int fildes"
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.Ft "char *"
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.Fn ptsname "int fildes"
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.Ft int
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.Fn unlockpt "int fildes"
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.Sh DESCRIPTION
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The
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.Fn grantpt ,
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.Fn ptsname ,
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and
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.Fn unlockpt
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functions allow access to pseudo-terminal devices.
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These three functions accept a file descriptor that references the
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master half of a pseudo-terminal pair.
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This file descriptor is created with
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.Xr posix_openpt 2 .
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.Pp
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The
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.Fn grantpt
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function is used to establish ownership and permissions
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of the slave device counterpart to the master device
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specified with
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.Fa fildes .
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The slave device's ownership is set to the real user ID
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of the calling process, and the permissions are set to
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user readable-writable and group writable.
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The group owner of the slave device is also set to the
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group
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.Dq Li tty .
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.Pp
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The
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.Fn ptsname
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function returns the full pathname of the slave device
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counterpart to the master device specified with
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.Fa fildes .
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This value can be used
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to subsequently open the appropriate slave after
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.Xr posix_openpt 2
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and
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.Fn grantpt
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have been called.
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.Pp
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The
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.Fn unlockpt
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function clears the lock held on the pseudo-terminal pair
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for the master device specified with
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.Fa fildes .
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.Sh RETURN VALUES
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.Rv -std grantpt unlockpt
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.Pp
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The
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.Fn ptsname
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function returns a pointer to the name
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of the slave device on success; otherwise a
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.Dv NULL
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pointer is returned.
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.Sh ERRORS
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The
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.Fn grantpt
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and
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.Fn unlockpt
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functions may fail and set
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.Va errno
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to:
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.Bl -tag -width Er
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.It Bq Er EBADF
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.Fa fildes
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is not a valid open file descriptor.
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.It Bq Er EINVAL
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.Fa fildes
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is not a master pseudo-terminal device.
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.El
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.Pp
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In addition, the
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.Fn grantpt
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function may set
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.Va errno
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to:
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.Bl -tag -width Er
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.It Bq Er EACCES
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The slave pseudo-terminal device could not be accessed.
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.El
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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 STANDARDS
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The
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.Fn ptsname
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function conforms to
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.St -p1003.1-2008 .
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.Pp
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This implementation of
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.Fn grantpt
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and
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.Fn unlockpt
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does not conform to
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.St -p1003.1-2008 ,
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because it depends on
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.Xr posix_openpt 2
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to create the pseudo-terminal device with proper permissions in place.
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It only validates whether
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.Fa fildes
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is a valid pseudo-terminal master device.
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Future revisions of the specification will likely allow this behaviour,
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as stated by the Austin Group.
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.Sh HISTORY
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The
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.Fn grantpt ,
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.Fn ptsname
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and
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.Fn unlockpt
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functions appeared in
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.Fx 5.0 .
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