std::chrono是C++11引入的标准库，用于时间的计算和处理。它按照ISO8601标准定义了多个时间类，例如：duration（持续时间）、time_point（时间点）和clock（时钟）。以下是一些常见的用法：

1. 计算程序运行时间

#include <iostream>
#include <string>
#include <chrono>
#include <unistd.h>
#include <sstream>
#include <iomanip>
#include <thread>int main(int argc, char *argv[])
{  //1. 计算耗时auto start = std::chrono::system_clock::now();//std::chrono::time_point start = std::chrono::system_clock::now();int32_t j = 0;for(int i=0;i<10000;i++){j++;}        //sleep(1);std::this_thread::sleep_for(std::chrono::seconds(1));auto end = std::chrono::system_clock::now();auto diff1 = std::chrono::duration_cast<std::chrono::seconds>(end - start).count();         //秒auto diff2 = std::chrono::duration_cast<std::chrono::milliseconds>(end - start).count();    //毫秒auto diff3 = std::chrono::duration_cast<std::chrono::microseconds> (end - start).count();   //微妙auto diff4 = std::chrono::duration_cast<std::chrono::nanoseconds>(end - start).count();     //纳秒//std::chrono::minutes//std::chrono::hours    std::cout<<"diff1 is: "<<diff1<<std::endl;std::cout<<"diff2 is: "<<diff2<<std::endl;std::cout<<"diff3 is: "<<diff3<<std::endl;std::cout<<"diff4 is: "<<diff4<<std::endl;return 0;
}

输出

diff1 is: 1
diff2 is: 1001
diff3 is: 1001608
diff4 is: 1001608504

2. 等待时间

线程的等待时间

std::this_thread::sleep_for(std::chrono::seconds(1));

3. 获取当前时间以及时间转换

获取当前时间

auto nowTime = std::chrono::system_clock::now();
std::time_t t = std::chrono::system_clock::to_time_t(nowTime);
std::cout << "nowTime is: " << std::ctime(&t) << std::endl;    

输出

nowTime is: Fri Jun  9 08:01:18 2023

时间转换
在工作中上述的时间不是我们需要的，通常用到的时间为string和int类型：

类型	说明
2023-06-09 08:01:18	string类型
1686297678	int64类型（秒级，10位）
1686297678549	int64类型（毫秒级，13位）
1686297678549829	int64类型（微妙级，16位）
1686297678549829794	int64类型（纳秒级，19位）

时间类型的转换

转换类型	转换类型
time_point -> string	time_point -> int64
string -> time_point	string -> int64
int64 -> string	int64 -> time_point

测试demo

time_conversion.hpp文件的下载地址

/** @brief: example about time format conversion by chrono* @data: 2023/06/09* @complie: g++ -g main.cc time_conversion.hpp -o d -std=c++11* @author: guokerenjian* @lastEditDate: */#include <iostream>
#include "time_conversion.hpp"using namespace t_convert;int main()
{TimeConvert tc;auto nowTime = std::chrono::system_clock::now();std::time_t t = std::chrono::system_clock::to_time_t(nowTime);std::cout << "nowTime is: " << std::ctime(&t) << std::endl;    //1.time_point -> stringstd::cout<<"time_point -> string"<<std::endl;std::string strTime;if(tc.timePointToString(nowTime, strTime)){std::cout<<"strTime is: "<<strTime<<"\n\n";}else{std::cout<<"failure"<<std::endl;}    //2.time_point -> int64std::cout<<"time_point -> int64"<<std::endl;int64_t itime{0};if(tc.timePointToInt64(nowTime, itime, TIME_TYPE::SECOND_TIME))  //秒{std::cout<<"itime is: "<<itime<<"\n";    }if(tc.timePointToInt64(nowTime, itime, TIME_TYPE::MILLISSECOND_TIME))  //毫秒{std::cout<<"itime is: "<<itime<<"\n";    }if(tc.timePointToInt64(nowTime, itime, TIME_TYPE::MICROSECOND_TIME))  //微妙{std::cout<<"itime is: "<<itime<<"\n";    }if(tc.timePointToInt64(nowTime, itime, TIME_TYPE::NANOSECOND_TIME))  //纳秒{std::cout<<"itime is: "<<itime<<"\n\n";    }    //3.string -> time_pointstd::cout<<"string -> time_point"<<std::endl;decltype(nowTime) resultTime;if(tc.stringToTimePoint(strTime, resultTime)){std::time_t t_result = std::chrono::system_clock::to_time_t(resultTime);std::cout << "resultTime is: " << std::ctime(&t_result) <<"\n\n";}    //4.string -> int64std::cout<<"string -> int64"<<std::endl;int64_t time_int{0};if(tc.stringToInt64(strTime, time_int)){std::cout<<"time_int is: "<<time_int<<"\n\n";}//5.int64 -> time_pointstd::cout<<"int64 -> time_point"<<std::endl;decltype(nowTime) resultTimeFromeInt;    int64_t time_test{0};if(tc.timePointToInt64(nowTime, time_test, TIME_TYPE::UNKOWN) && tc.Int64ToTimePoint(time_test,resultTimeFromeInt)){std::time_t t_result_int = std::chrono::system_clock::to_time_t(resultTimeFromeInt);std::cout << "t_result_int is: " << std::ctime(&t_result_int) <<"\n";}if(tc.timePointToInt64(nowTime, time_test, TIME_TYPE::MILLISSECOND_TIME) && tc.Int64ToTimePoint(time_test,resultTimeFromeInt)){std::time_t t_result_int = std::chrono::system_clock::to_time_t(resultTimeFromeInt);std::cout << "t_result_int is: " << std::ctime(&t_result_int) <<"\n";}if(tc.timePointToInt64(nowTime, time_test, TIME_TYPE::MICROSECOND_TIME) && tc.Int64ToTimePoint(time_test,resultTimeFromeInt)){std::time_t t_result_int = std::chrono::system_clock::to_time_t(resultTimeFromeInt);std::cout << "t_result_int is: " << std::ctime(&t_result_int) <<"\n";}if(tc.timePointToInt64(nowTime, time_test, TIME_TYPE::NANOSECOND_TIME) && tc.Int64ToTimePoint(time_test,resultTimeFromeInt)){std::time_t t_result_int = std::chrono::system_clock::to_time_t(resultTimeFromeInt);std::cout << "t_result_int is: " << std::ctime(&t_result_int) <<"\n\n";}//6.time_point -> stringstd::cout<<"time_point -> string"<<std::endl;std::string str_time_result;if(tc.Int64ToString(time_test, str_time_result)){std::cout<<"str_time_result is: "<<str_time_result<<std::endl;}    return 0;
}