The gzgets() function shall attempt to read data from the compressed file stream file, uncompressing it into buf until either len-1 bytes have been inserted into buf, or until a newline character has been uncompressed into buf. A null byte shall be appended to the uncompressed data. The file shall have been opened in for reading (see gzopen() and gzdopen()).
On success, gzgets() shall return a pointer to buf. Otherwise, gzgets() shall return Z_NULL. Applications may examine the cause using gzerror().
On error, gzgets() shall return Z_NULL. The following conditions shall always be treated as an error:
|file is |
|buf is |
|len is less than or equal to zero.|