升压C 的时期时间/时间格式

Question

在linux中，我正在从"/proc/stat"中读取时代的时间为btime，我想通过c boost转换为可读的日期和时间格式。

我尝试了以下事物，日期正常工作。

    time_t btime_ = 1505790902; //This is epoch time read from "/proc/stat" file.
    std::wstring currentDate_ = L"";
    boost::gregorian::date current_date_ = 
             boost::posix_time::from_time_t(btime_).date();
    std::wstring year_ = boost::lexical_cast<std::wstring>
                                         (current_date_.year());
    std::wstring day_ = boost::lexical_cast<std::wstring>
                                         (current_date_.day());

在这里，我每年都能正确。但是，我如何从上面的时代获得时间（HH :: MM：SS）？让我提示 - 我可以尝试。

预先感谢。

Answer 1

仅：

活在coliru

#include <ctime>
#include <boost/date_time/posix_time/posix_time_io.hpp>
int main() {
    std::time_t btime_ = 1505790902; //This is epoch time read from "/proc/stat" file.
    std::cout << boost::posix_time::from_time_t(btime_) << "n";
    std::cout.imbue(std::locale(std::cout.getloc(), new boost::posix_time::time_facet("%H:%M:%S")));
    std::cout << boost::posix_time::from_time_t(btime_) << "n";
}

打印

2017-Sep-19 03:15:02
03:15:02

更新

评论：

活在coliru

#include <boost/date_time/posix_time/posix_time_io.hpp>
#include <boost/date_time/c_local_time_adjustor.hpp>
namespace pt = boost::posix_time;
namespace g  = boost::gregorian;
using local_adj = boost::date_time::c_local_adjustor<pt::ptime>;
int main() {
    std::cout.imbue(std::locale(std::cout.getloc(), new pt::time_facet("%H:%M:%S")));
    std::time_t btime_ = 1505790902; // This is epoch time read from "/proc/stat" file.
    pt::ptime const timestamp = pt::from_time_t(btime_);
    std::cout << timestamp << "n";
    // This local adjustor depends on the machine TZ settings
    std::cout << local_adj::utc_to_local(timestamp) << " local timen";
}

打印

+ TZ=CEST
+ ./a.out
03:15:02
03:15:02 local time
+ TZ=MST
+ ./a.out
03:15:02
20:15:02 local time

Answer 2

您可以使用time_facet。这是打印UTC日期/时间的示例：

std::string PrintDateTime()
{
    std::stringstream str;
    boost::posix_time::time_facet *facet = new boost::posix_time::time_facet("%d.%m.%Y-%H:%M:%S-UTC");
    str.imbue(std::locale(str.getloc(), facet));
    str << boost::posix_time::second_clock::universal_time(); //your time point goes here
    return str.str();
}

请注意，您不必担心facet的内存管理。它已经从Boost内完成了。