Example

> tmp_file()
rlab-181200.1
> tmp_file()
rlab-181210.2
> tmp_file()
rlab-181218.3
> tmp_file()
rlab-181247.4
> load("/usr/local/lib/rlab/rlib/tmp_file.r"); a = tmp_file() ...
> load("/usr/local/lib/rlab/rlib/tmp_file.r"); b = tmp_file()
 a =
rlab-181524.1
 b =
rlab-181524.1