dataconn
FILE *dataconn (const char *);
din = dataconn ("r");
dout = dataconn(rmode);
dout = dataconn(name, st.st_size, "w");
din = dataconn(name, (off_t)-1, "r");
static FILE *dataconn (const char *, off_t, const char *);
dout = dataconn(file, -1, "w");
dout = dataconn("file list", (off_t)-1, "w");
dout = dataconn("file list", (off_t)-1, "w");