The clock measures the time since program start. Thus, the output is identical to the output of the clock boost::chrono::high_resolution_clock is based on.īoost::chrono::process_real_cpu_clock returns the CPU time a process has been running. The clock is only available if the macro BOOST_CHRONO_HAS_CLOCK_STEADY is defined.īoost::chrono::high_resolution_clock is a type definition for boost::chrono::system_clock or boost::chrono::steady_clock, depending on which clock measures time more precisely. The reference point could change with a different implementation.īoost::chrono::steady_clock isn’t supported on all platforms. However, starting the measurement since the last boot is an implementation detail. boost::chrono::steady_clock measures the time elapsed since the last boot. The message looks like the following: 10594369282958 nanoseconds since boot. This time is known as monotonic time.Įxample 37.1 displays the number of nanoseconds since the system was booted. Even if the time is set back on a computer, boost::chrono::steady_clock will return a later time. to_time_t() is a static member function that returns the current system time as the number of seconds since 1 January 1970 as a std::time_t.īoost::chrono::steady_clock is a clock that will always return a later time when it is accessed later. However, if you specifically want to get the time since 1 January 1970, call to_time_t(). The epoch 1 January 1970, which is used in these examples, is implementation dependent. The epoch isn’t standardized for boost::chrono::system_clock. Example 37.1 writes a string to standard output that looks like the following: 13919594042183544 seconds since Jan 1, 1970. If you change the time on your computer, boost::chrono::system_clock returns the new time. This is the time usually displayed on the desktop of your computer. Example 37.1 writes the epoch for every timepoint displayed.īoost.Chrono includes the following clocks:īoost::chrono::system_clock returns the system time. This reference timepoint is called epoch. All timepoints are relative to a universally valid timepoint. All clocks have in common the member function now(), which returns a timepoint. Std::cout << thread_clock::now() << ' ' Įxample 37.1 introduces all of the clocks provided by Boost.Chrono. Std::cout << process_system_cpu_clock::now() << ' ' Std::cout << process_user_cpu_clock::now() << ' ' Std::cout << process_real_cpu_clock::now() << ' ' Std::cout << high_resolution_clock::now() << ' '

Clock to milliseconds