cpp/chrono/c/clock

Returns the approximate processor time used by the process since the beginning of an implementation-defined era related to the program's execution. To convert result value to seconds divide it by clocks_per_sec.

Only the difference between two values returned by different calls to is meaningful, as the beginning of the  era does not have to coincide with the start of the program. time may advance faster or slower than the wall clock, depending on the execution resources given to the program by the operating system. For example, if the CPU is shared by other processes, time may advance slower than wall clock. On the other hand, if the current process is multithreaded and more than one execution core is available, time may advance faster than wall clock.

Parameters
(none)

Return value
Processor time used by the program so far or if that information is unavailable or its value cannot be represented.

Exceptions
Throws nothing.