Opens a gzip (.gz) file for reading or writing. The mode parameter is as in fopen() ("rb" or "wb") but can also include a compression level ("wb9") or a strategy: 'f' for filtered data as in "wb6f", 'h' for Huffman only compression as in "wb1h". (See the description of deflateInit2 in zlib.h for more information about the strategy parameter.)
Gzopen() can be used to read a file which is not in gzip format; in this case gzread() will directly read from the file without decompression.
Gzopen() returns a file pointer to the file opened, after that, everything you read from this file descriptor will be transparently decompressed and what you write gets compressed.
If the open fails, the function returns false.
You can use the optional third parameter and set it to "1", if you want to search for the file in the include_path, too.
See also gzclose().