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| author | Jacob McDonnell <jacob@jacobmcdonnell.com> | 2026-04-25 19:55:15 -0400 |
|---|---|---|
| committer | Jacob McDonnell <jacob@jacobmcdonnell.com> | 2026-04-25 19:55:15 -0400 |
| commit | 253e67c8b3a72b3a4757fdbc5845297628db0a4a (patch) | |
| tree | adf53b66087aa30dfbf8bf391a1dadb044c3bf4d /static/netbsd/man2/shmctl.2 | |
| parent | a9157ce950dfe2fc30795d43b9d79b9d1bffc48b (diff) | |
docs: Added All NetBSD Manuals
Diffstat (limited to 'static/netbsd/man2/shmctl.2')
| -rw-r--r-- | static/netbsd/man2/shmctl.2 | 205 |
1 files changed, 205 insertions, 0 deletions
diff --git a/static/netbsd/man2/shmctl.2 b/static/netbsd/man2/shmctl.2 new file mode 100644 index 00000000..9c5fcf9d --- /dev/null +++ b/static/netbsd/man2/shmctl.2 @@ -0,0 +1,205 @@ +.\" $NetBSD: shmctl.2,v 1.22 2026/01/02 22:22:22 nia Exp $ +.\" +.\" Copyright (c) 1995 Frank van der Linden +.\" All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" 3. The name of the author may not be used to endorse or promote products +.\" derived from this software without specific prior written permission +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR +.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES +.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. +.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, +.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT +.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, +.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY +.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT +.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF +.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. +.\" +.Dd November 25, 2006 +.Dt SHMCTL 2 +.Os +.Sh NAME +.Nm shmctl +.Nd shared memory control operations +.Sh LIBRARY +.Lb libc +.Sh SYNOPSIS +.In sys/shm.h +.Ft int +.Fn shmctl "int shmid" "int cmd" "struct shmid_ds *buf" +.Sh DESCRIPTION +The +.Fn shmctl +system call performs control operations on the shared memory segment +specified by +.Fa shmid . +.Pp +Each shared memory segment has a +.Sy shmid_ds +structure associated with it which contains the following members: +.Bd -literal + struct ipc_perm shm_perm; /* operation permissions */ + size_t shm_segsz; /* size of segment in bytes */ + pid_t shm_lpid; /* pid of last shm op */ + pid_t shm_cpid; /* pid of creator */ + shmatt_t shm_nattch; /* # of current attaches */ + time_t shm_atime; /* last shmat() time */ + time_t shm_dtime; /* last shmdt() time */ + time_t shm_ctime; /* last change by shmctl() */ +.Ed +.Pp +The +.Sy ipc_perm +structure used inside the +.Sy shmid_ds +structure is defined in +.In sys/ipc.h +and contains the following members: +.Bd -literal + uid_t cuid; /* creator user id */ + gid_t cgid; /* creator group id */ + uid_t uid; /* user id */ + gid_t gid; /* group id */ + mode_t mode; /* permission (lower 9 bits) */ +.Ed +.Pp +The operation to be performed by +.Fn shmctl +is specified in +.Fa cmd +and is one of: +.Bl -tag -width IPC_RMIDX +.It Dv IPC_STAT +Gather information about the shared memory segment and place it in the +structure pointed to by +.Fa buf . +.It Dv IPC_SET +Set the value of the +.Va shm_perm.uid , +.Va shm_perm.gid +and +.Va shm_perm.mode +fields in the structure associated with +.Fa shmid . +The values are taken from the corresponding fields in the structure +pointed to by +.Fa buf . +This operation can only be executed by the super-user, or a process that +has an effective user id equal to either +.Va shm_perm.cuid +or +.Va shm_perm.uid +in the data structure associated with the shared memory segment. +.It Dv IPC_RMID +Remove the shared memory segment specified by +.Fa shmid +and destroy the data associated with it. +Only the super-user or a process with an effective uid equal to the +.Va shm_perm.cuid +or +.Va shm_perm.uid +values in the data structure associated with the segment can do this. +.It Dv SHM_LOCK +Lock the shared memory segment specified by +.Fa shmid +in memory. +This operation can only be executed by the super-user. +.It Dv SHM_UNLOCK +Unlock the shared memory segment specified by +.Fa shmid . +This operation can only be executed by the super-user. +.El +.Pp +The read and write permissions on a shared memory identifier +are determined by the +.Va shm_perm.mode +field in the same way as is +done with files (see +.Xr chmod 2 ) , +but the effective uid can match either the +.Va shm_perm.cuid +field or the +.Va shm_perm.uid +field, and the +effective gid can match either +.Va shm_perm.cgid +or +.Va shm_perm.gid . +.Sh RETURN VALUES +Upon successful completion, a value of 0 is returned. +Otherwise, \-1 is returned and the global variable +.Va errno +is set to indicate the error. +.Sh ERRORS +.Fn shmctl +will fail if: +.Bl -tag -width Er +.It Bq Er EACCES +The command is +.Dv IPC_STAT +and the caller has no read permission for this shared memory segment. +.It Bq Er EFAULT +.Fa buf +specifies an invalid address. +.It Bq Er EINVAL +.Fa shmid +is not a valid shared memory segment identifier. +.Pp +.Va cmd +is not a valid command. +.It Bq Er ENOMEM +The +.Fa cmd +is equal to +.Dv SHM_LOCK +and there is not enough physical memory. +.It Bq Er EPERM +.Fa cmd +is equal to +.Dv IPC_SET +or +.Dv IPC_RMID +and the caller is not the super-user, nor does +the effective uid match either the +.Va shm_perm.uid +or +.Va shm_perm.cuid +fields of the data structure associated with the shared memory segment. +.Pp +An attempt was made to increase the value of +.Va shm_qbytes +through +.Dv IPC_SET +but the caller is not the super-user. +.Pp +The +.Fa cmd +is equal to +.Dv SHM_LOCK +or +.Dv SHM_UNLOCK +and the caller is not the super-user. +.El +.Sh SEE ALSO +.Xr ipcrm 1 , +.Xr ipcs 1 , +.Xr shmat 2 , +.Xr shmget 2 +.Sh STANDARDS +The +.Nm +system call conforms to +.St -xsh5 . +.Sh HISTORY +Shared memory segments appeared in the first release of +.At V . |
