pipebuf
struct pipebuf *bp = &rpipe->pipe_buffer;
struct pipebuf *bp;
struct pipebuf pipe_buffer; /* data storage */
char pipebuf[1];
pipebuf[0] = sigio_caught;
write(pd[1], pipebuf, sizeof(pipebuf));
r = read(pd[0], pipebuf, sizeof(pipebuf));
DPRINTF(" > child's sigio_cauht = %d\n", pipebuf[0]);
XP_EQ(0, pipebuf[0]);