++-使用boost :: posix_time计算时间差

Question

I need help to find out the difference between two given time as string. I'm using boost::posix_time and constructing the ptime object from boost::gregorian::date but i'm getting 0 when i'm trying to calculate the time_duration.

Here is the program

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

int main(int argc, char** argv) {

  std::string date_1 = "2014-08-15 10:12:10";
  std::string date_2 = "2014-08-15 16:40:02";

  boost::posix_time::ptime t1(boost::gregorian::from_simple_string(date_1));
  boost::posix_time::ptime t2(boost::gregorian::from_simple_string(date_2));

  boost::posix_time::time_duration td = t2 - t1;

  std::cout << boost::posix_time::to_simple_string(td) << std::endl;



}

This prints out 00:00:00

How to fix this and get the actual time duration.

Answer 1

As Martin alluded to in his comment, you used the wrong (date-only) constructor.

Here is a repaired version, along with some test output:

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

int main(int argc, char** argv) {

  std::string date_1 = "2014-08-15 10:12:10";
  std::string date_2 = "2014-08-15 16:40:02";

  boost::posix_time::ptime t1(boost::posix_time::time_from_string(date_1));
  boost::posix_time::ptime t2(boost::posix_time::time_from_string(date_2));

  std::cout << "t1: " << t1 << std::endl;
  std::cout << "t2: " << t2 << std::endl;

  boost::posix_time::time_duration td = t2 - t1;

  std::cout << boost::posix_time::to_simple_string(td) << std::endl;
}

which produces the desired result:

edd@max:/tmp$ g++ -o bdt bdt.cpp -lboost_date_time
edd@max:/tmp$ ./bdt
t1: 2014-Aug-15 10:12:10
t2: 2014-Aug-15 16:40:02
06:27:52
edd@max:/tmp$