feobp
needprompt = aret == F_SEEK && fseekp == feobp;
fseekp = feobp = fblocks = 0;
needprompt = intty && fseekp == feobp && aret == F_SEEK;
if (fseekp < fbobp || fseekp > feobp) {
fbobp = feobp = fseekp;
if (fseekp == feobp) {
fbobp = feobp;
feobp += c;
if (fseekp >= feobp) {
buf = (int) feobp / BUFSIZ;
off = (int) feobp % BUFSIZ;
feobp = fseekp = fblocks * BUFSIZ;
feobp += c;
feobp -= BUFSIZ * sb;
fseekp = feobp;
fseekp = fbobp = feobp = lseek(SHIN, (off_t) 0, SEEK_CUR);