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ptsname may set errno, so avoid saving and restoring errno across the function. PR: standards/171572
162 lines
4.2 KiB
Groff
162 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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.\" OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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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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.\" PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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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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.Dt PTSNAME 3
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.Os
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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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.Fn ptsname
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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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