Returns the string value associated with key under group_name.
Unlike get_value, this function handles escape sequences like \s.
In the event the key cannot be found, null is returned and throws
is set to KEY_NOT_FOUND. In the event that the
group_name cannot be found, null is returned and throws
is set to GROUP_NOT_FOUND.
| this |
a KeyFile |
| group_name |
a group name |
| key |
a key |
|
a newly allocated string or null if the specified key cannot be found. |