msgsnd man page on SmartOS

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MSGSND(2)							     MSGSND(2)

       msgsnd - message send operation

       #include <sys/msg.h>

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

       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 mes‐
       sage, and then a data portion that will hold the data bytes of the mes‐
       sage.  The structure below is an example of what this user-defined buf‐
       fer 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 calling process will return immediately.

	   o	  If (msgflg&IPC_NOWAIT) is 0, the calling process  will  sus‐
		  pend 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  pre‐
		      scribed 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

	   o	  msg_stime is set equal to the current time.

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

       The msgsnd() function will fail if:

		 Operation permission is denied to the	calling	 process.  See

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

		 The message queue identifier msgid is removed from  the  sys‐

		 The msgsnd() function was interrupted by a signal.

		 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:

		  The msgp argument points to an illegal address.

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

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

       │Interface Stability │ Standard	      │

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

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

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

				 Feb 11, 2003			     MSGSND(2)

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