NAME¶

std::chrono::operator<<(std::chrono::duration) - std::chrono::operator<<(std::chrono::duration)

Synopsis¶

Defined in header <chrono>
template<

class CharT,
class Traits,
class Rep, (since C++20)
class Period
> std::basic_ostream<CharT, Traits>&
operator<<( std::basic_ostream<CharT, Traits>& os,

const std::chrono::duration<Rep, Period>& d );

Inserts a textual representation of d into os.

Behaves as if it was implemented as

std::basic_ostringstream<CharT, Traits> s;
s.flags(os.flags());
s.imbue(os.getloc());
s.precision(os.precision());
s << d.count() << units_suffix; // see below
return os << s.str();

In other words, the stream flags, locale, and precision are determined by the
stream, but any padding are determined using the entire output string.

The units_suffix is determined based on Period::type according to the following
table.

Period::type Suffix
std::atto as
std::femto fs
std::pico ps
std::nano ns
std::micro µs (U+00B5) or us, it is implementation-defined which one is
used
std::milli ms
std::centi cs
std::deci ds
std::ratio<1> s
std::deca das
std::hecto hs
std::kilo ks
std::mega Ms
std::giga Gs
std::tera Ts
std::peta Ps
std::exa Es
std::ratio<60> min
std::ratio<3600> h
std::ratio<86400> d
None of the above, and [num]s
Period::type::den == 1
None of the above [num/den]s

For the last two rows of the table, num and den in the suffix are Period::type::num
and Period::type::den formatted as a decimal number with no leading zeroes,
respectively.

Return value¶

A reference to the stream, i.e., os.

Example¶

This example shows the output of std::chrono::operator<< when given a duration:

// Run this code

#include <chrono>
#include <iostream>
using namespace std::chrono_literals;

int main()
{
constexpr auto duration = 123ms;
std::cout << duration << '\n';
}

Output:¶

123ms

See also¶

format stores formatted representation of the
(C++20) arguments in a new string
(function template)
std::formatter<std::chrono::duration> formatting support for duration
(C++20) (class template specialization)
operator<< performs stream input and output on strings
operator>> (function template)
to_string converts an integral or floating-point value
(C++11) to string
(function)
to_wstring converts an integral or floating-point value
(C++11) to wstring
(function)