usr/src/sys/sys/msgbuf.h

/*
 * Copyright (c) 1982 Regents of the University of California.
 * All rights reserved.  The Berkeley software License Agreement
 * specifies the terms and conditions for redistribution.
 *
 *      @(#)msgbuf.h    6.3 (Berkeley) %G%
 */

#define MSG_MAGIC       0x063061
#define MSG_BSIZE       (4096 - 3 * sizeof (long))
struct  msgbuf {
        long    msg_magic;
        long    msg_bufx;
        long    msg_bufr;
        char    msg_bufc[MSG_BSIZE];
};
#ifdef KERNEL
struct  msgbuf msgbuf;
#endif