1 .\" $NetBSD: msgrcv.2,v 1.1 1995/10/16 23:49:20 jtc Exp $
3 .\" Copyright (c) 1995 Frank van der Linden
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38 .Nd receive a message from a message queue
46 .Fn msgrcv "int msqid" "void *msgp" "size_t msgsz" "long msgtyp" "int msgflg"
50 function receives a message from the message queue specified in
52 and places it into the structure pointed to by
54 This structure should consist of the following members:
56 long mtype; /* message type */
57 char mtext[1]; /* body of message */
61 is an integer greater than 0 that can be used for selecting messages,
63 is an array of bytes, with a size up to that of the system limit
68 has one of the following meanings:
75 The first message of type
83 The first message on the queue will be received.
89 The first message of the lowest message type that is
90 less than or equal to the absolute value of
98 specifies the maximum length of the requested message.
100 message has a length greater than
102 it will be silently truncated if the
106 otherwise an error will be returned.
108 If no matching message is present on the message queue specified by
112 depends on whether the
121 will immediately return a value of -1, and set
127 is not set, the calling process will be blocked
131 A message of the requested type becomes available on the message queue.
133 The message queue is removed, in which case -1 will be returned, and
138 A signal is received and caught.
145 If a message is successfully received, the data structure associated with
147 is updated as follows:
151 is decremented by the size of the message.
154 is set to the pid of the caller.
157 is set to the current time.
163 Upon successful completion,
165 returns the number of bytes received into the
167 field of the structure pointed to by
169 Otherwise, -1 is returned, and
171 set to indicate the error.
182 is not a valid message queue identifier.
184 The message queue was removed while
186 was waiting for a message of the requested type to become available on it.
193 A matching message was received, but its size was greater than
200 The calling process does not have read access to the message queue.
205 points to an invalid address.
207 The system call was interrupted by the delivery of a signal.
209 There is no message of the requested type available on the message queue,
220 Message queues appeared in the first release of