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OpenSolaris 2009.06 - man page for msgsnd (opensolaris section 2)

msgsnd(2)				   System Calls 				msgsnd(2)

NAME
       msgsnd - message send operation

SYNOPSIS
       #include <sys/msg.h>

       int msgsnd(int msqid, const void *msgp, size_t msgsz, int msgflg);

DESCRIPTION
       The  msgsnd()  function is used to send a message to the queue associated with the message
       queue identifier specified by msqid.

       The msgp argument points to a user-defined buffer that must contain first a field of  type
       long int that will specify the type of the message, and then a data portion that will hold
       the data bytes of the message. The structure below is an example of what this user-defined
       buffer might look like:

	 struct  mymsg {
		 long  mtype;	  /* message type */
		 char  mtext[1];  /* message text */
	 }

       The  mtype  member  is a non-zero positive type long int that can be used by the receiving
       process for message selection.

       The mtext member is any text of length msgsz bytes. The msgsz argument can range from 0 to
       a system-imposed maximum.

       The  msgflg  argument specifies the action to be taken if one or more of the following are
       true:

	   o	  The number of bytes already on the queue is equal to msg_qbytes. See Intro(2).

	   o	  The total number of messages on the queue would exceed the maximum  allowed  by
		  the system. See NOTES.

       These actions are as follows:

	   o	  If  (msgflg&IPC_NOWAIT) is non-zero, the message will not be sent and the call-
		  ing process will return immediately.

	   o	  If (msgflg&IPC_NOWAIT) is 0, the calling process will suspend  execution  until
		  one of the following occurs:

	       o      The  condition  responsible  for	the suspension no longer exists, in which
		      case the message is sent.

	       o      The message  queue  identifier  msqid  is  removed  from	the  system  (see
		      msgctl(2));  when  this  occurs,	errno  is  set	equal  to EIDRM and -1 is
		      returned.

	       o      The calling process receives a signal that is to be caught;  in  this  case
		      the  message  is	not sent and the calling process resumes execution in the
		      manner prescribed in sigaction(2).

       Upon successful completion, the following actions are  taken  with  respect  to	the  data
       structure associated with msqid (see Intro(2)):

	   o	  msg_qnum is incremented by 1.

	   o	  msg_lspid is set equal to the process ID of the calling process.

	   o	  msg_stime is set equal to the current time.

RETURN VALUES
       Upon  successful completion, 0 is returned. Otherwise, -1 is returned, no message is sent,
       and errno is set to indicate the error.

ERRORS
       The msgsnd() function will fail if:

       EACCES	 Operation permission is denied to the calling process. See Intro(2).

       EAGAIN	 The  message  cannot  be  sent  for  one  of  the  reasons   cited   above   and
		 (msgflg&IPC_NOWAIT) is non-zero.

       EIDRM	 The message queue identifier msgid is removed from the system.

       EINTR	 The msgsnd() function was interrupted by a signal.

       EINVAL	 The  value  of  msqid	is  not a valid message queue identifier, or the value of
		 mtype is less than 1.

		 The value of msgsz is less than 0 or greater than the system-imposed limit.

       The msgsnd() function may fail if:

	EFAULT	  The msgp argument points to an illegal address.

USAGE
       The value passed as the msgp argument should be converted to type void *.

ATTRIBUTES
       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+

SEE ALSO
       rctladm(1M),  Intro(2),	msgctl(2),  msgget(2),	 msgrcv(2),   setrctl(2),   sigaction(2),
       attributes(5), standards(5)

NOTES
       The maximum number of messages allowed on a message queue is the minimum enforced value of
       the process.max-msg-messages  resource  control	of  the  creating  process  at	the  time
       msgget(2) was used to allocate the queue.

	See rctladm(1M) and setrctl(2) for information about using resource controls.

SunOS 5.11				   11 Feb 2003					msgsnd(2)


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