zopen
if ((fp = zopen(path, gzmode)) == NULL) {
extern FILE *zopen(const char *fname, const char *mode);
if ((fp = zopen(path, gzmode)) == NULL) {
FILE *zopen(const char *fname, const char *mode);
if ((ofp = zopen(out, "w", bits)) == NULL) {
if ((ifp = zopen(in, "r", bits)) == NULL) {
extern FILE *zopen(const char *fname, const char *mode, int bits);
FILE *zopen(const char *, const char *, int);