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using boost.date_time to get time in millisecond microsecond level

Guide

format flags

second millisecond microsecond nanosecond

Format Flags

• %f
  
  Fractional seconds are always used, even when their value is zero
  
  "13:15:16.000000"

• %F *
  
  Fractional seconds are used only when their value is not zero.
  
  "13:15:16"
  
  "05:04:03.001234"

to string

The Boost.Date_Time library provides the following ptime to std::string conversions within the boost::posix_time namespace:

• std::string to_simple_string(ptime) returns a string in the form of YYYY-mmm-DD HH:MM:SS.fffffffff format where mmm is the three character month name.
• std::string to_iso_string(ptime) returns a string in the form of YYYYMMDDTHHMMSS,fffffffff where T is the date-time separator.
• std::string to_iso_extended_string(ptime) returns a string in the form of YYYY-MM-DDTHH:MM:SS,fffffffff where T is the date-time separator.

date_time.cpp

#include <iostream>

#include <sstream>

#include <boost/date_time/posix_time/posix_time.hpp>

#include <boost/date_time/gregorian/gregorian.hpp>

using namespace std;

using namespace boost::posix_time;

using namespace boost::gregorian;

/*

second millisecond microsecond nanosecond

Format Flags

%f

Fractional seconds are always used, even when their value is zero

"13:15:16.000000"

%F *

Fractional seconds are used only when their value is not zero.

"13:15:16"

"05:04:03.001234"

*/

std::string ptime_2_str_name(boost::posix_time::ptime now)

{

	// https://*.com/questions/5018188/how-to-format-a-datetime-to-string-using-boost

	// for multiple use

	std::stringstream ss;

	//static std::locale loc(std::cout.getloc(), new time_facet("%Y%m%d_%H%M%S_%f"));

	static std::locale loc(ss.getloc(), new time_facet("%Y%m%d_%H%M%S_%f"));

	ss.imbue(loc);

	ss << now;

	return ss.str(); // 20180118_111501_208797

}

std::string str_name_2_iso_format(std::string str_name)

{

	/*

	20180118_111501_208797 ===> 20180118T111501.208797===>from_iso_string===>ptime

	*/

	//std::cout << "time length: " << str_ptime.length() << endl; //22

	size_t first_pos = str_name.find_first_of('_');

	size_t second_pos = str_name.find_last_of('_');

	str_name[first_pos] = 'T';

	str_name[second_pos] = '.';

	return str_name;

}

ptime from_name_string(std::string str_ptime)

{

	std::string str_iso_ptime = str_name_2_iso_format(str_ptime);

	return from_iso_string(str_iso_ptime);

}

int main()

{

	ptime p1(date(2001, 1, 1), hours(1));

	ptime p2 = time_from_string("2002-2-2 02:00:00.999888"); // fraction part: 6 bits

	ptime p3 = from_iso_string("20030303T031233.777666");    // fraction part: 6 bits

	ptime p4 = second_clock::local_time();                   // in second

	ptime p5 = microsec_clock::universal_time();             // UTC World time in millisecond,microsecond

	ptime p6 = microsec_clock::local_time();                 // UTC local time in millisecond,microsecond           

	cout << p1 << endl

		<< p2 << endl

		<< p3 << endl

		<< p4 << endl

		<< p5 << endl

		<< p6 << endl << endl;

	/*

	* date()

	* time_of_day()

	*/

	date d = p1.date();

	time_duration td = p1.time_of_day();

	cout << d << ", " << td << endl << endl;

	cout << to_simple_string(p2) << endl               //YYYY-mmm-DD HH:MM:SS.ffffff

		<< to_iso_string(p2) << endl               //YYYYMMDDTHHMMSS,ffffff

		<< to_iso_extended_string(p2) << endl;     //YYYY-MM-DDTHH:MM:SS,ffffff  

	cout << "User defined format time:" << endl;

	std::string str_name = ptime_2_str_name(p6);

	ptime p7 = from_name_string(str_name);

	cout <<"                      p6: "<< ptime_2_str_name(p6) << endl;

	cout <<"p7 from String2Ptime(p6): "<< ptime_2_str_name(p7) << endl;

	return 0;

}

CMakeLists.txt

# Specify the minimum version for CMake

cmake_minimum_required(VERSION 2.8)

# Project's name

project(date_time)

# Set the output folder where your program will be created

set(CMAKE_BINARY_DIR ${CMAKE_SOURCE_DIR}/bin)

set(EXECUTABLE_OUTPUT_PATH ${CMAKE_BINARY_DIR})

set(LIBRARY_OUTPUT_PATH ${CMAKE_BINARY_DIR})

#find_package(Boost 1.5.8 REQUIRED COMPONENTS date_time system filesystem iostreams)

find_package(Boost 1.5.8 REQUIRED COMPONENTS date_time)

include_directories(${Boost_INCLUDE_DIRS})

link_directories(${Boost_LIBRARY_DIRS})

# The following folder will be included

include_directories("${PROJECT_SOURCE_DIR}")

add_executable(date_time ${PROJECT_SOURCE_DIR}/date_time.cpp)

target_link_libraries(date_time ${Boost_LIBRARIES})

run and output

compile program and run

mkdir build

cd build

cmake ..

make 

cd bin

./date_time

output

2001-Jan-01 01:00:00

2002-Feb-02 02:00:00.999888

2003-Mar-03 03:12:33.777666

2018-Jan-18 15:20:47

2018-Jan-18 07:20:47.815415

2018-Jan-18 15:20:47.815419

2001-Jan-01, 01:00:00

2002-Feb-02 02:00:00.999888

20020202T020000.999888

2002-02-02T02:00:00.999888

User defined format time:

                      p6: 20180118_152047_815419

p7 from String2Ptime(p6): 20180118_152047_815419

Reference

• boost datetime
• how-to-format-a-datetime-to-string-using-boost
• boost ptime tostring

History

• 20180118: created.

Copyright

• Post author: kezunlin
• Post link: https://kezunlin.me/post/107cbcbb/
• Copyright Notice: All articles in this blog are licensed under CC BY-NC-SA 3.0 unless stating additionally.