Open a new logfile. Messages will only appear in the logfile
if their level
exceeds the log's loglevel
;
this allows you to easily change the amount of detail being logged.
Re-opening a logfile will erase the previous output unless append
is TRUE. Opening a new logfile when one is already open will temporarily
switch logging to that new file.
If sink
is TRUE, all screen output will be captured (via sink
).