Programming Interfaces Guide

Initializing a Message Queue

msgget(2) initializes a new message queue. It can also return the message queue ID (msqid) of the queue corresponding to the key argument. The value passed as the msgflg argument must be an octal integer with settings for the queue's permissions and control flags.

The MSGMNI kernel configuration option determines the maximum number of unique message queues that the kernel supports. msgget(2) fails when this limit is exceeded.

The following code illustrates msgget(2).

#include <sys/ipc.h>
#include <sys/msg.h>
        key_t    key;         /* key to be passed to msgget() */
        int      msgflg,      /* msgflg to be passed to msgget() */
                 msqid;       /* return value from msgget() */
        key = ...
        msgflg = ...
        if ((msqid = msgget(key, msgflg)) == -1)
               perror("msgget: msgget failed");
        } else
               (void) fprintf(stderr, "msgget succeeded");