std::chrono::system_clock::now

 

C++

Language

Standard library headers

Concepts

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

 

Utilities library

Type support (basic types, RTTI, type traits)

Dynamic memory management

Error handling

Program utilities

Variadic functions

Date and time

Function objects

initializer_list (C++11)

bitset

hash (C++11)

Relational operators

rel_ops::operator!=rel_ops::operator>rel_ops::operator<=rel_ops::operator>=

Pairs and tuples

pair

tuple (C++11)

piecewise_construct_t (C++11)

piecewise_construct (C++11)

Swap, forward and move

swap

forward (C++11)

move (C++11)

move_if_noexcept (C++11)

declval (C++11)

 

Date and time utilities

time_point (C++11)

duration (C++11)

system_clock (C++11)

steady_clock (C++11)

high_resolution_clock (C++11)

C-style date and time

 

std::chrono::system_clock

Member functions

system_clock::now

system_clock::to_time_t

system_clock::from_time_t

 

static std::chrono::time_point<std::chrono::system_clock> now();		(since C++11)

Returns a time point representing with the current point in time.

Parameters

(none)

Return value

A time point representing the current time.

Exceptions

noexcept specification:  

noexcept

  

Example

Run this code

#include <iostream>
#include <vector>
#include <chrono>
 
int main()
{
    for (unsigned long long size = 1; size < 10000000; size *= 10) {
 
        auto start = std::chrono::system_clock::now();   // a "timepoint" representing now
 
        std::vector<int> v(size, 42);               // something that takes some time to do
 
        auto end = std::chrono::system_clock::now();     // the new current "timepoint"
 
        auto elapsed = end - start;                 // difference is a "duration"
 
        std::cout << size << ": " << elapsed.count() << '\n';  // clock ticks (seconds)
    }
}

Possible output:

1: 1
10: 2
100: 3
1000: 6
10000: 47
100000: 507
1000000: 4822