C++ 日期格式化

datetime_format.cpp

#include <chrono>
#include <ctime>
#include <iostream>
#include <string>

/**
 * date format to string
 * https://cplusplus.com/reference/ctime/strftime/
 */

std::string datetime_format(std::time_t time, const std::string& format, std::size_t sz = 20) {
  std::string datetime(sz, '\0');
  std::strftime(&datetime[0], datetime.size(), format.data(), std::localtime(&time));
  return datetime;
}

std::string curr_format(const std::string& format, std::size_t sz = 20) {
  typedef std::chrono::system_clock Clock;
  return datetime_format(Clock::to_time_t(Clock::now()), format, sz);
}

int main() {
  typedef std::chrono::system_clock Clock;
  std::time_t now{Clock::to_time_t(Clock::now())};

  std::cout << curr_format("现在是 %F %T", 50).c_str() << '\n';
  std::cout << datetime_format(now, "现在是 %F").c_str() << '\n';
  std::cout << datetime_format(now, "现在是 %T").c_str() << '\n';

  return 0;
}