1.\" Copyright (c) 2019 The FreeBSD Foundation, Inc. 2.\" 3.\" This documentation was written by 4.\" Konstantin Belousov <kib@FreeBSD.org> under sponsorship 5.\" from the FreeBSD Foundation. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" $FreeBSD$ 29.\" 30.Dd May 30, 2019 31.Dt POSIXSHMCONTROL 1 32.Os 33.Sh NAME 34.Nm posixshmcontrol 35.Nd Control POSIX shared memory segments 36.Sh SYNOPSIS 37.Nm 38.Ar create 39.Op Fl m Ar mode 40.Op Pa path \&... 41.Nm 42.Ar rm 43.Op Pa path \&... 44.Nm 45.Ar ls 46.Op Fl h 47.Op Fl n 48.Nm 49.Ar dump 50.Op Pa path \&... 51.Nm 52.Ar stat 53.Op Fl h 54.Op Fl n 55.Op Pa path \&... 56.Nm 57.Ar truncate 58.Op Fl s Ar length 59.Op Pa path \&... 60.Sh DESCRIPTION 61The 62.Nm 63command manipulates the named POSIX shared memory segments. 64It allows inspecting existing segments, dumping their metadata or contents, 65and unlinking them. 66.Pp 67Unlinking removes the name from the system and, when the last process 68unmaps the segment and closes file descriptor pointing to the segment, 69frees underlying memory. 70.Pp 71The number of hard links as displayed by the 72.Ic stat 73subcommand, is equal to the number of references to the underlying VM 74object. 75It is almost always equal to the number of mappings +1, except 76for transient references. 77.Pp 78The following subcommands are provided: 79.Bl -tag -width truncate 80.It Ic create 81Create segments with the specified paths, if not exist. 82The 83.Ar mode 84optional numerical argument specifies initial access mode. 85.It Ic rm 86Unlink the paths specified. 87.It Ic ls 88List all linked named shared memory segments visible to the caller. 89For each segment, the user and group owner, size, and path are displayed. 90.It Ic dump 91Output raw bytes values from the segment to standard output. 92.It Ic stat 93Print metadata for the specified path, in the format similar to the 94.Xr stat 1 95utility. 96.It Ic truncate 97Change the length of the segments. 98Argument to the 99.Fl s 100option specifies new length. 101The human-friendly 'k', 'm', 'g' suffixes can be used, see 102.Xr expand_number 3. 103If the option is not specified, assumed length is zero. 104.El 105.Pp 106For some commands, the following options may be provided: 107.Bl -tag -width XXX 108.It Fl h 109If specified, requests human-readable display of size, see 110.Xr humanize_number 3 . 111.It Fl n 112Prevent translation of owner and group into symbolic names 113using name-switch services, instead the raw numeric values are printed. 114.El 115.Sh EXIT STATUS 116.Ex -std 117.Sh EXAMPLES 118.Bl -bullet 119.It 120To show content of the shared memory segment with the path 121.Pa /1 , 122use the command 123.Dl "posixshmcontrol dump /q | hexdump -C" 124.It 125To create a segment with the path 126.Pa /2 127and then enlarge it to 1M, use the sequence of commands 128.Dl "posixshmcontrol create /2" 129.Dl "posixshmcontrol truncate -s 1m /2" 130.El 131.Sh SEE ALSO 132.Xr hexdump 1 , 133.Xr stat 1 , 134.Xr ftruncate 2 , 135.Xr read 2 , 136.Xr shm_open 2 , 137.Xr shm_unlink 2 , 138.Xr stat 2 , 139.Xr expand_number 3 , 140.Xr humanize_number 3 , 141.Xr sysctl 3 142.Sh HISTORY 143The 144.Nm 145command appeared in 146.Fx 13.0 . 147.Sh AUTHORS 148The 149.Nm 150command and this manual page were written by 151.An Konstantin Belousov Aq Mt kib@freebsd.org 152under sponsorship from The FreeBSD Foundation. 153