std::chrono::file_clock::now

 

C++

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General utilities Date and time Function objects Formatting library (C++20) bitset hash (C++11) Relational operators (deprecated in C++20) rel_ops::operator!=rel_ops::operator> rel_ops::operator<=rel_ops::operator>= Integer comparison functions cmp_equalcmp_lesscmp_less_than (C++20)(C++20)(C++20)    cmp_not_equalcmp_greatercmp_greater_than (C++20)(C++20)(C++20) in_range (C++20) Swap and type operations swap ranges::swap (C++20) exchange (C++14) declval (C++11) to_underlying (C++23) forward (C++11) forward_like (C++23) move (C++11) move_if_noexcept (C++11) as_const (C++17) Common vocabulary types pair tuple (C++11) optional (C++17) any (C++17) variant (C++17) tuple_size (C++11) tuple_element (C++11) apply (C++17) make_from_tuple (C++17) expected (C++23) Elementary string conversions to_chars (C++17) from_chars (C++17) chars_format (C++17)

 

Date and time utilities

Time point
time_point (C++11)	clock_time_conversion (C++20)	clock_cast (C++20)
Duration
duration (C++11)
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system_clock (C++11) steady_clock (C++11) high_resolution_clock (C++11)	is_clock (C++20) utc_clock (C++20) tai_clock (C++20)	gps_clock (C++20) file_clock (C++20) local_t (C++20)
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chrono I/O
parse (C++20)
C-style date and time

 

std::chrono::file_clock

Member functions

file_clock::now

file_clock::to_sysfile_clock::from_sys (provided only if to_utc and from_utc are not provided)

file_clock::to_utcfile_clock::from_utc (provided only if to_sys and from_sys are not provided)

Time point I/O

operator<<

formatter<std::chrono::file_time>

from_stream

 

static std::chrono::time_point<std::chrono::file_clock> now() noexcept;		(since C++20)

Returns a time point representing the current point in time.

Parameters

(none)

Return value

A time point representing the current time.

Example

Run this code

#include <iostream>
#include <iomanip>
#include <vector>
#include <numeric>
#include <chrono>
 
volatile int sink;
int main()
{
    std::cout << std::fixed << std::setprecision(9) << std::left;
    for (auto size = 1ull; size < 1000'000'000ull; size *= 100) {
        // record start time
        auto start = std::chrono::file_clock::now();
        // do some work
        std::vector<int> v(size, 42);
        sink = std::accumulate(v.begin(), v.end(), 0u); // make sure it's a side effect
        // record end time
        auto end = std::chrono::file_clock::now();
        std::chrono::duration<double> diff = end - start;
        std::cout << "Time to fill and iterate a vector of " << std::setw(9)
                  << size << " ints : " << diff.count() << " s\n";
    }
}

Possible output:

Time to fill and iterate a vector of 1         ints : 0.000006568 s
Time to fill and iterate a vector of 100       ints : 0.000002854 s
Time to fill and iterate a vector of 10000     ints : 0.000116290 s
Time to fill and iterate a vector of 1000000   ints : 0.011742752 s
Time to fill and iterate a vector of 100000000 ints : 0.505534949 s