1msgctl(2)                        System Calls                        msgctl(2)
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NAME

6       msgctl - message control operations
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SYNOPSIS

9       #include <sys/msg.h>
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11       int msgctl(int msqid, int cmd, struct msqid_ds *buf);
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DESCRIPTION

15       The  msgctl() function provides a variety of message control operations
16       as specified by cmd. The following cmds are available:
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18       IPC_STAT    Place the current value of each member of the  data  struc‐
19                   ture associated with msqid into the structure pointed to by
20                   buf.  The  contents  of  this  structure  are  defined   in
21                   Intro(2).
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24       IPC_SET     Set  the  value of the following members of the data struc‐
25                   ture associated with msqid to the corresponding value found
26                   in the structure pointed to by buf:
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28                     msg_perm.uid
29                     msg_perm.gid
30                     msg_perm.mode /* access permission bits only */
31                     msg_qbytes
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33                   This  command  can  be  executed only by a process that has
34                   either the {PRIV_IPC_OWNER} privilege or an effective  user
35                   ID  equal  to the value of msg_perm.cuid or msg_perm.uid in
36                   the data structure associated with msqid.  Only  a  process
37                   with  the  {PRIV_SYS_IPC_CONFIG}  privilege  can  raise the
38                   value of msg_qbytes.
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41       IPC_RMID    Remove the message queue identifier specified by msqid from
42                   the system and destroy the message queue and data structure
43                   associated with it. This cmd can  only  be  executed  by  a
44                   process that has an effective user ID either with appropri‐
45                   ate privileges asserted in the effective set  or  equal  to
46                   the  value  of  msg_perm.cuid  or  msg_perm.uid in the data
47                   structure  associated  with  msqid.  The  buf  argument  is
48                   ignored.
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RETURN VALUES

52       Upon  successful  completion, msgctl() returns 0. Otherwise, it returns
53       −1 and sets errno to indicate the error.
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ERRORS

56       The msgctl() function will fail if:
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58       EACCES       The cmd argument is IPC_STAT and operation  permission  is
59                    denied to the calling process (see Intro(2)).
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62       EFAULT       The buf argument points to an illegal address.
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65       EINVAL       The  msqid  argument  is not a valid message queue identi‐
66                    fier; or the cmd argument is not a  valid  command  or  is
67                    IPC_SET and msg_perm.uid or msg_perm.gid is not valid.
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70       EOVERFLOW    The  cmd  argument is IPC_STAT and uid or gid is too large
71                    to be stored in the structure pointed to by buf.
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74       EPERM        The   cmd   argument   is   IPC_RMID   or   IPC_SET,   the
75                    {PRIV_SYS_IPC_OWNER}  privilege  is  not  asserted  in the
76                    effective set of the calling process, and is not equal  to
77                    the  value  of  msg_perm.cuid  or msg_perm.uid in the data
78                    structure associated with msqid.
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80                    The cmd argument is IPC_SET, an attempt is being  made  to
81                    increase   to   the   value   of   msg_qbytes,   and   the
82                    {PRIV_SYS_IPC_CONFIG} privilege is  not  asserted  in  the
83                    effective set of the calling process.
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ATTRIBUTES

87       See attributes(5) for descriptions of the following attributes:
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92       ┌─────────────────────────────┬─────────────────────────────┐
93       │      ATTRIBUTE TYPE         │      ATTRIBUTE VALUE        │
94       ├─────────────────────────────┼─────────────────────────────┤
95       │Interface Stability          │Standard                     │
96       └─────────────────────────────┴─────────────────────────────┘
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SEE ALSO

99       Intro(2),   msgget(2),   msgrcv(2),  msgsnd(2),  attributes(5),  privi‐
100       leges(5), standards(5)
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104SunOS 5.11                        22 Mar 2004                        msgctl(2)
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