previousTime: value that indicates how the command should operate:
>=0: the function returns a time difference with previousTime. PreviousTime must have been previously retrieved with the -1 argument below.
-1: the function returns a time relative to an arbitrary time. Use this to measure time differences within CoppeliaSim
-2: the function returns a time as follows:
// On Windows:
// On MacOS / Linux:
struct timeval now;