This command will fail with non-zero status upon error. Some exit
codes are:
-- The config file is invalid (ret=3),
-- can not write to the config file (ret=4),
+- The section or key is invalid (ret=1),
- no section or name was provided (ret=2),
-- the section or key is invalid (ret=1),
+- the config file is invalid (ret=3),
+- the config file cannot be written (ret=4),
- you try to unset an option which does not exist (ret=5),
- you try to unset/set an option for which multiple lines match (ret=5), or
- you try to use an invalid regexp (ret=6).