|MSGSND(2)||System Calls Manual||MSGSND(2)|
msgsnd — send a
message to a message queue
msqid, const void
function sends a message to the message queue specified by
msqid. msgp points to a
structure containing the message. This structure should consist of the
long mtype; /* message type */ char mtext; /* body of message */
mtype is an integer greater than 0 that can
be used for selecting messages (see
mtext is an array of msgsz
bytes, with a size between 0 and that of the system limit
If the number of bytes already on the message queue
plus msgsz is bigger than the maximum number of bytes
on the message queue (msg_qbytes,
see msgctl(2)), or the number of messages on all queues system-wide is already equal to the system limit, msgflg determines the action of
If msgflg has
set in it, the call will return immediately. If msgflg
does not have
IPC_NOWAIT set in it, the call will
After a successful call, the data structure associated with the message queue is updated in the following way:
Upon successful completion, the value 0 is returned; otherwise the value -1 is returned and the global variable errno is set to indicate the error.
msgsnd() will fail if:
msgsz is greater than msg_qbytes.
IPC_NOWAITwas set in msgflg.
msgsnd() was waiting for a resource to become available in order to deliver the message.
Message queues appeared in AT&T System V Release 1 UNIX.
|December 10, 2014||OpenBSD-5.9|