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msgctl(2)

msgctl(2)                        System Calls                        msgctl(2)



NAME
       msgctl - 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  struc‐
                   ture 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 struc‐
                   ture 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  executed  by  a
                   process that has an effective user ID either with appropri‐
                   ate 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(7) for descriptions of the following attributes:


       tab()  box; cw(2.75i) |cw(2.75i) lw(2.75i) |lw(2.75i) ATTRIBUTE TYPEAT‐
       TRIBUTE  VALUE  _  Interface  StabilityCommitted  _  StandardSee  stan‐
       dards(7).


SEE ALSO
       msgrcv(2),   Intro(2),   msgget(2),  msgsnd(2),  attributes(7),  privi‐
       leges(7), standards(7)



Oracle Solaris 11.4               22 Mar 2004                        msgctl(2)
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