system v interprocess communication mechanisms

System V interprocess communication mechanisms

System V message queue

The msgsnd() and msgrcv() system calls are used, respectively, to send messages to, and receive messages from, a System V message queue. The calling process must have write permission on the message queue in order to send a message, and read permission to receive a message.

The msgp argument is a pointer to a caller-defined structure of the following general form:

struct msgbuf {
   long mtype;       /* message type, must be > 0 */
   char mtext[1];    /* message data */
};

The mtext field is an array (or other structure) whose size is specified by msgsz, a nonnegative integer value. Messages of zero length (i.e., no mtext field) are permitted. The mtype field must have a strictly positive integer value. This value can be used by the receiving process for message selection.