Check whether a configuration is currently active
is_active(config)Logical indicating whether the specified configuration is active
Configuration name
The name of the currently active configuration is read from the
R_CONFIG_ACTIVE environment variable. If the variable is
not defined then the "default" configuration is used.
To test for whether a configuration is active you should use the
is_active() function rather than inspecting the
environment variable directly (this is to so that tests remain
valid if other means of specifying configurations are introduced
in the future).