Get and set logging level
The logging level for httpuv can be set to report differing levels of
information. Possible logging levels (from least to most information
"DEBUG". The default level is
logLevel(level = NULL)
The logging level. Must be one of
NULL(the default), then this function simply returns the current logging level.
level=NULL, then this returns the current logging level. If
level is any other value, then this returns the previous logging
level, from before it is set to the new value.