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.\" $FreeBSD$ 27.\" 28.Dd July 17, 1995 29.Dt SHMCTL 2 30.Os 31.Sh NAME 32.Nm shmctl 33.Nd shared memory control 34.Sh LIBRARY 35.Lb libc 36.Sh SYNOPSIS 37.In sys/types.h 38.In sys/ipc.h 39.In sys/shm.h 40.Ft int 41.Fn shmctl "int shmid" "int cmd" "struct shmid_ds *buf" 42.Sh DESCRIPTION 43Performs the action specified by 44.Fa cmd 45on the shared memory segment identified by 46.Fa shmid : 47.Bl -tag -width SHM_UNLOCKX 48.It Dv IPC_STAT 49Fetch the segment's 50.Fa "struct shmid_ds" , 51storing it in the memory pointed to by 52.Fa buf . 53.\" 54.\" XXX need to make sure that this is correct for FreeBSD 55.\" 56.It Dv IPC_SET 57Changes the 58.Fa shm_perm.uid , 59.Fa shm_perm.gid , 60and 61.Fa shm_perm.mode 62members of the segment's 63.Fa "struct shmid_ds" 64to match those of the struct pointed to by 65.Fa buf . 66The calling process's effective uid must 67match either 68.Fa shm_perm.uid 69or 70.Fa shm_perm.cuid , 71or it must have superuser privileges. 72.It Dv IPC_RMID 73Removes the segment from the system. 74The removal will not take 75effect until all processes having attached the segment have exited; 76however, once the IPC_RMID operation has taken place, no further 77processes will be allowed to attach the segment. 78For 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.Vt shmid_ds 94structure 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 is straight from sys/shm.h 98.\" 99.Bd -literal 100struct shmid_ds { 101 struct ipc_perm shm_perm; /* operation permission structure */ 102 size_t 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 int 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}; 110.Ed 111.Sh RETURN VALUES 112.Rv -std shmctl 113.Sh ERRORS 114The 115.Fn shmctl 116system call 117will fail if: 118.Bl -tag -width Er 119.It Bq Er EINVAL 120Invalid operation, or 121no shared memory segment was found corresponding to 122.Fa shmid . 123.\" 124.\" XXX I think the following is right: ipcperm() only returns EPERM 125.\" when an attempt is made to modify (IPC_M) by a non-creator 126.\" non-owner 127.It Bq Er EPERM 128The calling process's effective uid does not match the uid of 129the shared memory segment's owner or creator. 130.It Bq Er EACCES 131Permission denied due to mismatch between operation and mode of 132shared memory segment. 133.El 134.Sh "SEE ALSO" 135.Xr shmat 2 , 136.Xr shmdt 2 , 137.Xr shmget 2 , 138.Xr ftok 3 139