2019-05-29 13:51:18 +00:00
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.\" Copyright (c) 2019 The FreeBSD Foundation, Inc.
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.\"
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.\" This documentation was written by
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.\" Konstantin Belousov <kib@FreeBSD.org> under sponsorship
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.\" from the FreeBSD Foundation.
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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 AUTHORS 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 AUTHORS 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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2019-05-30 16:02:40 +00:00
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.Dd May 30, 2019
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2019-05-29 13:51:18 +00:00
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.Dt POSIXSHMCONTROL 1
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.Os
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.Sh NAME
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.Nm posixshmcontrol
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.Nd Control POSIX shared memory segments
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.Sh SYNOPSIS
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.Nm
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.Ar create
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.Op Fl m Ar mode
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.Op Pa path \&...
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.Nm
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.Ar rm
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.Op Pa path \&...
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.Nm
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.Ar ls
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.Op Fl h
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.Op Fl n
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.Nm
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.Ar dump
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.Op Pa path \&...
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.Nm
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.Ar stat
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.Op Fl h
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.Op Fl n
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.Op Pa path \&...
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.Nm
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.Ar truncate
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.Op Fl s Ar length
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.Op Pa path \&...
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.Sh DESCRIPTION
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The
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.Nm
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command manipulates the named POSIX shared memory segments.
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It allows inspecting existing segments, dumping their metadata or contents,
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and unlinking them.
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.Pp
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Unlinking removes the name from the system and, when the last process
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unmaps the segment and closes file descriptor pointing to the segment,
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frees underlying memory.
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.Pp
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The number of hard links as displayed by the
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.Ic stat
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subcommand, is equal to the number of references to the underlying VM
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object.
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It is almost always equal to the number of mappings +1, except
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for transient references.
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.Pp
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The following subcommands are provided:
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.Bl -tag -width truncate
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.It Ic create
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Create segments with the specified paths, if not exist.
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The
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.Ar mode
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optional numerical argument specifies initial access mode.
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.It Ic rm
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Unlink the paths specified.
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.It Ic ls
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List all linked named shared memory segments visible to the caller.
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For each segment, the user and group owner, size, and path are displayed.
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.It Ic dump
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Output raw bytes values from the segment to standard output.
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.It Ic stat
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Print metadata for the specified path, in the format similar to the
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.Xr stat 1
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utility.
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.It Ic truncate
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Change the length of the segments.
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Argument to the
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.Fl s
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option specifies new length.
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The human-friendly 'k', 'm', 'g' suffixes can be used, see
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.Xr expand_number 3.
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If the option is not specified, assumed length is zero.
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.El
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.Pp
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For some commands, the following options may be provided:
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.Bl -tag -width XXX
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.It Fl h
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If specified, requests human-readable display of size, see
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.Xr humanize_number 3 .
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.It Fl n
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Prevent translation of owner and group into symbolic names
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using name-switch services, instead the raw numeric values are printed.
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.El
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.Sh EXIT STATUS
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.Ex -std
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.Sh EXAMPLES
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.Bl -bullet
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.It
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To show content of the shared memory segment with the path
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.Pa /1 ,
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use the command
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.Dl "posixshmcontrol dump /q | hexdump -C"
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.It
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To create a segment with the path
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.Pa /2
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and then enlarge it to 1M, use the sequence of commands
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.Dl "posixshmcontrol create /2"
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.Dl "posixshmcontrol truncate -s 1m /2"
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.El
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.Sh SEE ALSO
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.Xr hexdump 1 ,
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.Xr stat 1 ,
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.Xr ftruncate 2 ,
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.Xr read 2 ,
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.Xr shm_open 2 ,
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.Xr shm_unlink 2 ,
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.Xr stat 2 ,
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.Xr expand_number 3 ,
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.Xr humanize_number 3 ,
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.Xr sysctl 3
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.Sh HISTORY
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The
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.Nm
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command appeared in
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.Fx 13.0 .
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.Sh AUTHORS
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The
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.Nm
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command and this manual page were written by
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.An Konstantin Belousov Aq Mt kib@freebsd.org
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under sponsorship from The FreeBSD Foundation.
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