1.\" 2.\" Copyright (c) 1995 David Hovemeyer <daveho@infocom.com> 3.\" 4.\" All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR 16.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT, 19.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25.\" 26.\" $FreeBSD: src/lib/libc/sys/shmctl.2,v 1.9.2.4 2001/12/14 18:34:01 ru Exp $ 27.\" $DragonFly: src/lib/libc/sys/shmctl.2,v 1.2 2003/06/17 04:26:47 dillon Exp $ 28.\" 29.Dd July 17, 1995 30.Dt SHMCTL 2 31.Os 32.Sh NAME 33.Nm shmctl 34.Nd shared memory control 35.Sh LIBRARY 36.Lb libc 37.Sh SYNOPSIS 38.In machine/param.h 39.In sys/types.h 40.In sys/ipc.h 41.In sys/shm.h 42.Ft int 43.Fn shmctl "int shmid" "int cmd" "struct shmid_ds *buf" 44.Sh DESCRIPTION 45Performs the action specified by 46.Fa cmd 47on the shared memory segment identified by 48.Fa shmid : 49.Bl -tag -width SHM_UNLOCKX 50.It Dv IPC_STAT 51Fetch the segment's 52.Fa "struct shmid_ds" , 53storing it in the memory pointed to by 54.Fa buf . 55.\" 56.\" XXX need to make sure that this is correct for FreeBSD 57.\" 58.It Dv IPC_SET 59Changes the 60.Fa shm_perm.uid , 61.Fa shm_perm.gid , 62and 63.Fa shm_perm.mode 64members of the segment's 65.Fa "struct shmid_ds" 66to match those of the struct pointed to by 67.Fa buf . 68The calling process's effective uid must 69match either 70.Fa shm_perm.uid 71or 72.Fa shm_perm.cuid , 73or it must have superuser privileges. 74.It Dv IPC_RMID 75Removes the segment from the system. The removal will not take 76effect until all processes having attached the segment have exited; 77however, once the IPC_RMID operation has taken place, no further 78processes will be allowed to attach the segment. For the operation 79to succeed, the calling process's effective uid must match 80.Fa shm_perm.uid 81or 82.Fa shm_perm.cuid , 83or the process must have superuser privileges. 84.\" .It Dv SHM_LOCK 85.\" Locks the segment in memory. The calling process must have 86.\" superuser privileges. Not implemented in FreeBSD. 87.\" .It Dv SHM_UNLOCK 88.\" Unlocks the segment from memory. The calling process must 89.\" have superuser privileges. Not implemented in FreeBSD. 90.El 91.Pp 92The 93.Fa shmid_ds 94struct is defined as follows: 95.\" 96.\" I fiddled with the spaces a bit to make it fit well when viewed 97.\" with nroff, but otherwise it's straight from sys/shm.h 98.\" 99.Bd -literal 100struct shmid_ds { 101 struct ipc_perm shm_perm; /* operation permission structure */ 102 int shm_segsz; /* size of segment in bytes */ 103 pid_t shm_lpid; /* process ID of last shared memory op */ 104 pid_t shm_cpid; /* process ID of creator */ 105 short shm_nattch; /* number of current attaches */ 106 time_t shm_atime; /* time of last shmat() */ 107 time_t shm_dtime; /* time of last shmdt() */ 108 time_t shm_ctime; /* time of last change by shmctl() */ 109 void *shm_internal; /* sysv stupidity */ 110}; 111.Ed 112.Sh RETURN VALUES 113.Rv -std shmctl 114.Sh ERRORS 115.Fn Shmctl 116will fail if: 117.Bl -tag -width Er 118.It Bq Er EINVAL 119Invalid operation, or 120no shared memory segment was found corresponding to 121.Fa shmid . 122.\" 123.\" XXX I think the following is right: ipcperm() only returns EPERM 124.\" when an attempt is made to modify (IPC_M) by a non-creator 125.\" non-owner 126.It Bq Er EPERM 127The calling process's effective uid does not match the uid of 128the shared memory segment's owner or creator. 129.It Bq Er EACCES 130Permission denied due to mismatch between operation and mode of 131shared memory segment. 132.El 133.Sh "SEE ALSO" 134.Xr shmat 2 , 135.Xr shmdt 2 , 136.Xr shmget 2 , 137.Xr ftok 3 138