2 .\" Copyright (c) 1995 David Hovemeyer <daveho@infocom.com>
4 .\" All rights reserved.
6 .\" Redistribution and use in source and binary forms, with or without
7 .\" modification, are permitted provided that the following conditions
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15 .\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
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33 .Nd shared memory control
42 .Fn shmctl "int shmid" "int cmd" "struct shmid_ds *buf"
44 Performs the action specified by
46 on the shared memory segment identified by
48 .Bl -tag -width SHM_UNLOCKX
51 .Fa "struct shmid_ds" ,
52 storing it in the memory pointed to by
55 .\" XXX need to make sure that this is correct for FreeBSD
63 members of the segment's
65 to match those of the struct pointed to by
67 The calling process's effective uid must
72 or it must have superuser privileges.
74 Removes the segment from the system.
75 The removal will not take
76 effect until all processes having attached the segment have exited;
77 however, once the IPC_RMID operation has taken place, no further
78 processes will be allowed to attach the segment.
80 to succeed, the calling process's effective uid must match
84 or the process must have superuser privileges.
86 .\" Locks the segment in memory. The calling process must have
87 .\" superuser privileges. Not implemented in FreeBSD.
89 .\" Unlocks the segment from memory. The calling process must
90 .\" have superuser privileges. Not implemented in FreeBSD.
95 structure is defined as follows:
97 .\" I fiddled with the spaces a bit to make it fit well when viewed
98 .\" with nroff, but otherwise it is straight from sys/shm.h
102 struct ipc_perm shm_perm; /* operation permission structure */
103 size_t shm_segsz; /* size of segment in bytes */
104 pid_t shm_lpid; /* process ID of last shared memory op */
105 pid_t shm_cpid; /* process ID of creator */
106 int shm_nattch; /* number of current attaches */
107 time_t shm_atime; /* time of last shmat() */
108 time_t shm_dtime; /* time of last shmdt() */
109 time_t shm_ctime; /* time of last change by shmctl() */
121 Invalid operation, or
122 no shared memory segment was found corresponding to
125 .\" XXX I think the following is right: ipcperm() only returns EPERM
126 .\" when an attempt is made to modify (IPC_M) by a non-creator
129 The calling process's effective uid does not match the uid of
130 the shared memory segment's owner or creator.
132 Permission denied due to mismatch between operation and mode of
133 shared memory segment.