gzopen
file = gzopen(fname, "rb");
file = gzopen(fname, "wb");
out = gzopen(outfile, mode);
in = gzopen(infile, "rb");
file = gzopen(*argv, "rb");
ZEXTERN gzFile ZEXPORT gzopen(const char *, const char *);
zfp = gzopen(*argv, "rb");
if ((in = gzopen(name, "r")) == NULL) {
gzFile gz = gzopen(fname, mode);
ZEXTERN gzFile ZEXPORT gzopen(const char *, const char *);