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Diffstat (limited to 'static/netbsd/man2/msgctl.2')
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diff --git a/static/netbsd/man2/msgctl.2 b/static/netbsd/man2/msgctl.2 new file mode 100644 index 00000000..a29c59b6 --- /dev/null +++ b/static/netbsd/man2/msgctl.2 @@ -0,0 +1,195 @@ +.\" $NetBSD: msgctl.2,v 1.16 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 August 25, 1999 +.Dt MSGCTL 2 +.Os +.Sh NAME +.Nm msgctl +.Nd message control operations +.Sh LIBRARY +.Lb libc +.Sh SYNOPSIS +.In sys/msg.h +.Ft int +.Fn msgctl "int msqid" "int cmd" "struct msqid_ds *buf" +.Sh DESCRIPTION +The +.Fn msgctl +system call performs control operations on the message queue specified +by +.Fa msqid . +.Pp +Each message queue has a +.Sy msqid_ds +structure associated with it which contains the following members: +.Bd -literal + struct ipc_perm msg_perm; /* msg queue permission bits */ + msgqnum_t msg_qnum; /* # of msgs in the queue */ + msglen_t msg_qbytes; /* max # of bytes on the queue */ + pid_t msg_lspid; /* pid of last msgsnd() */ + pid_t msg_lrpid; /* pid of last msgrcv() */ + time_t msg_stime; /* time of last msgsnd() */ + time_t msg_rtime; /* time of last msgrcv() */ + time_t msg_ctime; /* time of last msgctl() */ +.Ed +.Pp +The +.Sy ipc_perm +structure used inside the +.Sy msgid_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 msgctl +is specified in +.Fa cmd +and is one of: +.Bl -tag -width IPC_RMIDX +.It Dv IPC_STAT +Gather information about the message queue and place it in the +structure pointed to by +.Fa buf . +.It Dv IPC_SET +Set the value of the +.Va msg_perm.uid , +.Va msg_perm.gid , +.Va msg_perm.mode +and +.Va msg_qbytes +fields in the structure associated with +.Fa msqid . +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 msg_perm.cuid +or +.Va msg_perm.uid +in the data structure associated with the message queue. +The value of +.Va msg_qbytes +can only be increased by the super-user. +Values for +.Va msg_qbytes +that exceed the system limit +.Pf ( Dv MSGMNB +from +.In sys/msg.h ) +are silently truncated to that limit. +.It Dv IPC_RMID +Remove the message queue specified by +.Fa msqid +and destroy the data associated with it. +Only the super-user or a process with an effective uid equal to the +.Va msg_perm.cuid +or +.Va msg_perm.uid +values in the data structure associated with the queue can do this. +.El +.Pp +The permission to read from or write to a message queue (see +.Xr msgsnd 2 +and +.Xr msgrcv 2 ) +is determined by the +.Va msg_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 msg_perm.cuid +field or the +.Va msg_perm.uid +field, and the +effective gid can match either +.Va msg_perm.cgid +or +.Va msg_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 msgctl +will fail if: +.Bl -tag -width Er +.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 msg_perm.uid +or +.Va msg_perm.cuid +fields of the data structure associated with the message queue. +.Pp +An attempt was made to increase the value of +.Va msg_qbytes +through +.Dv IPC_SET , +but the caller is not the super-user. +.It Bq Er EACCES +.Fa cmd +is +.Dv IPC_STAT +and the caller has no read permission for this message queue. +.It Bq Er EINVAL +.Fa msqid +is not a valid message queue identifier. +.Pp +.Fa cmd +is not a valid command. +.It Bq Er EFAULT +.Fa buf +specifies an invalid address. +.El +.Sh SEE ALSO +.Xr msgget 2 , +.Xr msgrcv 2 , +.Xr msgsnd 2 +.Sh STANDARDS +The +.Nm +system call conforms to +.St -xsh5 . +.Sh HISTORY +Message queues appeared in the first release of +.At V . |