c++11 - How to convert std::chrono::time_point to string

C++11 - How to convert std::chrono::time_point to string

In C++11, converting std::chrono::time_point to a string involves several steps, primarily formatting the time point into a human-readable string representation. Here's a step-by-step guide on how to achieve this using C++11 features:

Example Scenario

Let's assume you have a std::chrono::time_point representing the current system time, and you want to convert it to a string format like "YYYY-MM-DD HH:MM":

#include <iostream> #include <chrono> #include <ctime> #include <iomanip> #include <sstream> // Alias for simplicity using namespace std::chrono; int main() { // Get current system time as time_point system_clock::time_point now = system_clock::now(); // Convert time_point to std::time_t std::time_t now_c = system_clock::to_time_t(now); // Convert std::time_t to std::tm (broken down time) std::tm now_tm = *std::localtime(&now_c); // Format std::tm into a string std::stringstream ss; ss << std::put_time(&now_tm, "%Y-%m-%d %H:%M:%S"); std::string time_str = ss.str(); // Print the formatted string std::cout << "Formatted time: " << time_str << std::endl; return 0; }

Explanation

  1. Get Current Time Point: system_clock::now() gives you the current time as a time_point.

  2. Convert to std::time_t: Use system_clock::to_time_t(now) to convert time_point to std::time_t, which is a type representing calendar time.

  3. Convert to std::tm: Use std::localtime(&now_c) to convert std::time_t to std::tm, which represents a broken-down time (year, month, day, hour, minute, second).

  4. Format into String: Use std::put_time with std::stringstream to format std::tm into a string with the desired format ("%Y-%m-%d %H:%M:%S").

  5. Output: Print or use time_str as needed.

Notes

  • Time Formatting: Adjust the format string ("%Y-%m-%d %H:%M:%S") according to your requirements. This example uses %Y for year, %m for month, %d for day, %H for hour in 24-hour format, %M for minute, and %S for second.

  • Time Zone: This example uses std::localtime, which converts to the local time zone. If you need UTC or another time zone, you may need to adjust the approach accordingly.

  • C++11 Features: std::chrono provides high-resolution clocks and time points, while <iomanip> and <sstream> are used for string formatting.

This method allows you to convert std::chrono::time_point to a formatted string efficiently using C++11 standard library features. Adjust as per your specific requirements, such as using UTC time or custom formatting options.

Examples

  1. Convert std::chrono::time_point to string using std::put_time

    • Description: How to convert a std::chrono::time_point to a string representation using std::put_time.
    • Code:
      #include <iostream> #include <iomanip> #include <ctime> #include <chrono> int main() { auto now = std::chrono::system_clock::now(); auto now_c = std::chrono::system_clock::to_time_t(now); std::cout << "Current time: " << std::put_time(std::localtime(&now_c), "%F %T") << std::endl; return 0; }
      Explanation: This code snippet demonstrates how to convert the current std::chrono::system_clock::time_point to a string using std::put_time with a format string "%F %T" for date and time in ISO 8601 format.

  2. Convert std::chrono::time_point to string using std::ctime

    • Description: Implementing conversion of std::chrono::time_point to a string using std::ctime.
    • Code:
      #include <iostream> #include <ctime> #include <chrono> int main() { auto now = std::chrono::system_clock::now(); std::time_t now_c = std::chrono::system_clock::to_time_t(now); std::cout << "Current time: " << std::ctime(&now_c); return 0; }
      Explanation: This code uses std::ctime to convert the std::chrono::system_clock::time_point to a C-style string format representing the current time.

  3. Convert std::chrono::time_point to string using std::strftime

    • Description: How to format std::chrono::time_point to a string using std::strftime.
    • Code:
      #include <iostream> #include <ctime> #include <chrono> int main() { auto now = std::chrono::system_clock::now(); std::time_t now_c = std::chrono::system_clock::to_time_t(now); char buffer[80]; std::strftime(buffer, sizeof(buffer), "%Y-%m-%d %H:%M:%S", std::localtime(&now_c)); std::cout << "Current time: " << buffer << std::endl; return 0; }
      Explanation: This code uses std::strftime to format the std::chrono::system_clock::time_point to a custom string format ("%Y-%m-%d %H:%M:%S" for example).

  4. Convert std::chrono::time_point to string using std::stringstream

    • Description: Implementing conversion of std::chrono::time_point to a string using std::stringstream.
    • Code:
      #include <iostream> #include <sstream> #include <chrono> int main() { auto now = std::chrono::system_clock::now(); std::time_t now_c = std::chrono::system_clock::to_time_t(now); std::stringstream ss; ss << std::put_time(std::localtime(&now_c), "%Y-%m-%d %H:%M:%S"); std::string str = ss.str(); std::cout << "Current time: " << str << std::endl; return 0; }
      Explanation: This code uses std::stringstream with std::put_time to convert the std::chrono::system_clock::time_point to a string.

  5. Convert std::chrono::time_point to string with custom duration

    • Description: How to convert std::chrono::time_point to a string representation with a custom duration.
    • Code:
      #include <iostream> #include <iomanip> #include <chrono> int main() { auto now = std::chrono::system_clock::now(); auto now_custom = std::chrono::duration_cast<std::chrono::seconds>(now.time_since_epoch()).count(); std::cout << "Current time in seconds since epoch: " << now_custom << std::endl; return 0; }
      Explanation: This code snippet converts the current std::chrono::system_clock::time_point to the number of seconds since the epoch.

  6. Convert std::chrono::time_point to string with milliseconds

    • Description: Implementing conversion of std::chrono::time_point to a string with milliseconds.
    • Code:
      #include <iostream> #include <iomanip> #include <chrono> int main() { auto now = std::chrono::system_clock::now(); auto now_ms = std::chrono::duration_cast<std::chrono::milliseconds>(now.time_since_epoch()).count(); std::cout << "Current time in milliseconds since epoch: " << now_ms << std::endl; return 0; }
      Explanation: This code snippet converts the current std::chrono::system_clock::time_point to the number of milliseconds since the epoch.

  7. Convert std::chrono::time_point to string with microseconds

    • Description: How to convert std::chrono::time_point to a string representation with microseconds.
    • Code:
      #include <iostream> #include <iomanip> #include <chrono> int main() { auto now = std::chrono::system_clock::now(); auto now_us = std::chrono::duration_cast<std::chrono::microseconds>(now.time_since_epoch()).count(); std::cout << "Current time in microseconds since epoch: " << now_us << std::endl; return 0; }
      Explanation: This code snippet converts the current std::chrono::system_clock::time_point to the number of microseconds since the epoch.

  8. Convert std::chrono::time_point to string with nanoseconds

    • Description: Implementing conversion of std::chrono::time_point to a string with nanoseconds.
    • Code:
      #include <iostream> #include <iomanip> #include <chrono> int main() { auto now = std::chrono::system_clock::now(); auto now_ns = std::chrono::duration_cast<std::chrono::nanoseconds>(now.time_since_epoch()).count(); std::cout << "Current time in nanoseconds since epoch: " << now_ns << std::endl; return 0; }
      Explanation: This code snippet converts the current std::chrono::system_clock::time_point to the number of nanoseconds since the epoch.

  9. Convert std::chrono::time_point to string with milliseconds precision

    • Description: How to convert std::chrono::time_point to a string representation with milliseconds precision.
    • Code:
      #include <iostream> #include <iomanip> #include <chrono> int main() { auto now = std::chrono::system_clock::now(); auto now_ms = std::chrono::duration_cast<std::chrono::milliseconds>(now.time_since_epoch()).count(); std::time_t now_t = std::chrono::system_clock::to_time_t(now); std::cout << "Current time: " << std::put_time(std::localtime(&now_t), "%F %T") << "." << std::setfill('0') << std::setw(3) << (now_ms % 1000) << std::endl; return 0; }
      Explanation: This code snippet converts the current std::chrono::system_clock::time_point to a string with milliseconds precision by appending milliseconds to the formatted time string.

  10. Convert std::chrono::time_point to string with custom format

    • Description: Implementing conversion of std::chrono::time_point to a string with a custom format.
    • Code:
      #include <iostream> #include <iomanip> #include <chrono> int main() { auto now = std::chrono::system_clock::now(); std::time_t now_t = std::chrono::system_clock::to_time_t(now); std::cout << "Current time: " << std::put_time(std::localtime(&now_t), "%Y-%m-%d %H:%M:%S") << std::endl; return 0; }
      Explanation: This code snippet converts the current std::chrono::system_clock::time_point to a string with a custom format ("%Y-%m-%d %H:%M:%S" for example) using std::put_time.

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