+ *
+ * 'file', 'line' and 'func' are indicators of position of the code in source files
+ * (see macros __FILE__, __LINE__ and __func__).
+ *
+ * 'level' is defined by syslog standard:
+ * EMERGENCY 0 System is unusable
+ * ALERT 1 Action must be taken immediately
+ * CRITICAL 2 Critical conditions
+ * ERROR 3 Error conditions
+ * WARNING 4 Warning conditions
+ * NOTICE 5 Normal but significant condition
+ * INFO 6 Informational
+ * DEBUG 7 Debug-level messages