msgctl(2) System Calls msgctl(2)NAMEmsgctl - message control operations
SYNOPSIS
#include <sys/msg.h>
int msgctl(int msqid, int cmd, struct msqid_ds *buf);
DESCRIPTION
The msgctl() function provides a variety of message control operations
as specified by cmd. The following cmds are available:
IPC_STAT Place the current value of each member of the data
structure associated with msqid into the structure
pointed to by buf. The contents of this structure are
defined in intro(2).
IPC_SET Set the value of the following members of the data
structure associated with msqid to the corresponding
value found in the structure pointed to by buf:
msg_perm.uid
msg_perm.gid
msg_perm.mode /* access permission bits only */
msg_qbytes
This command can be executed only by a process that has
either the {PRIV_IPC_OWNER} privilege or an effective
user ID equal to the value of msg_perm.cuid or
msg_perm.uid in the data structure associated with
msqid. Only a process with the {PRIV_SYS_IPC_CONFIG}
privilege can raise the value of msg_qbytes.
IPC_RMID Remove the message queue identifier specified by msqid
from the system and destroy the message queue and data
structure associated with it. This cmd can only be exe‐
cuted by a process that has an effective user ID either
with appropriate privileges asserted in the effective
set or equal to the value of msg_perm.cuid or
msg_perm.uid in the data structure associated with
msqid. The buf argument is ignored.
RETURN VALUES
Upon successful completion, msgctl() returns 0. Otherwise, it returns
−1 and sets errno to indicate the error.
ERRORS
The msgctl() function will fail if:
EACCES The cmd argument is IPC_STAT and operation permission
is denied to the calling process (see intro(2)).
EFAULT The buf argument points to an illegal address.
EINVAL The msqid argument is not a valid message queue identi‐
fier; or the cmd argument is not a valid command or is
IPC_SET and msg_perm.uid or msg_perm.gid is not valid.
EOVERFLOW The cmd argument is IPC_STAT and uid or gid is too
large to be stored in the structure pointed to by buf.
EPERM The cmd argument is IPC_RMID or IPC_SET, the
{PRIV_SYS_IPC_OWNER} privilege is not asserted in the
effective set of the calling process, and is not equal
to the value of msg_perm.cuid or msg_perm.uid in the
data structure associated with msqid.
The cmd argument is IPC_SET, an attempt is being made
to increase to the value of msg_qbytes, and the
{PRIV_SYS_IPC_CONFIG} privilege is not asserted in the
effective set of the calling process.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Interface Stability │Standard │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOintro(2), msgget(2), msgrcv(2), msgsnd(2), attributes(5), privi‐
leges(5), standards(5)SunOS 5.10 22 Mar 2004 msgctl(2)
