msgbuf_peekbytes
msgbuf_peekbytes(msgbufp, NULL, 0, &seq);
buflen = msgbuf_peekbytes(msgbufp, buf, sizeof(buf), &seq);
msgbuf_peekbytes(msgbufp, NULL, 0, &seq);
while ((len = msgbuf_peekbytes(msgbufp, buf, sizeof(buf), &seq)) > 0) {
msgbuf_peekbytes(msgbufp, NULL, 0, &seq);
len = msgbuf_peekbytes(msgbufp, buf, sizeof(buf), &seq);
int msgbuf_peekbytes(struct msgbuf *mbp, char *buf, int buflen,