written be appended to the file. "+" will result in an error, since reading
and writing to the same gzip file is not supported.
+ These functions, as well as gzip, will read and decode a sequence of gzip
+ streams in a file. The append function of gzopen() can be used to create
+ such a file. (Also see gzflush() for another way to do this.) When
+ appending, gzopen does not test whether the file begins with a gzip stream,
+ nor does it look for the end of the gzip streams to begin appending. gzopen
+ will simply append a gzip stream to the existing file.
+
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.