erdblk
ret = erdblk(cptr, len, fn);
ret = erdblk(cmsglen, sizeof(cmsglen), fn);
len = erdblk(bufr, (int) MIN(msglen, EBUFSIZ), fn);
len = erdblk((char *)&Nbytes, sizeof(Nbytes), fn);
len = erdblk(bufr, nread, fn);
extern int erdblk();