time_t seconds;
time(&seconds);
cout << seconds << endl;This gives me a timestamp. How can I get that epoch date into a string?
std::string s = seconds;does not work
29 Answers
Try std::stringstream.
#include <string>
#include <sstream>
std::stringstream ss;
ss << seconds;
std::string ts = ss.str();A nice wrapper around the above technique is Boost's lexical_cast:
#include <boost/lexical_cast.hpp>
#include <string>
std::string ts = boost::lexical_cast<std::string>(seconds);And for questions like this, I'm fond of linking The String Formatters of Manor Farm by Herb Sutter.
UPDATE:
With C++11, use to_string().
Try this if you want to have the time in a readable string:
#include <ctime>
std::time_t now = std::time(NULL);
std::tm * ptm = std::localtime(&now);
char buffer[32];
// Format: Mo, 15.06.2009 20:20:00
std::strftime(buffer, 32, "%a, %d.%m.%Y %H:%M:%S", ptm); For further reference of strftime() check out cppreference.com
1The top answer here does not work for me.
See the following examples demonstrating both the stringstream and lexical_cast answers as suggested:
#include <iostream>
#include <sstream>
int main(int argc, char** argv){ const char *time_details = "2017-01-27 06:35:12"; struct tm tm; strptime(time_details, "%Y-%m-%d %H:%M:%S", &tm); time_t t = mktime(&tm); std::stringstream stream; stream << t; std::cout << t << "/" << stream.str() << std::endl;
}Output: 1485498912/1485498912 Found here
#include <boost/lexical_cast.hpp>
#include <string>
int main(){ const char *time_details = "2017-01-27 06:35:12"; struct tm tm; strptime(time_details, "%Y-%m-%d %H:%M:%S", &tm); time_t t = mktime(&tm); std::string ts = boost::lexical_cast<std::string>(t); std::cout << t << "/" << ts << std::endl; return 0;
}Output: 1485498912/1485498912 Found: here
The 2nd highest rated solution works locally:
#include <iostream>
#include <string>
#include <ctime>
int main(){ const char *time_details = "2017-01-27 06:35:12"; struct tm tm; strptime(time_details, "%Y-%m-%d %H:%M:%S", &tm); time_t t = mktime(&tm); std::tm * ptm = std::localtime(&t); char buffer[32]; std::strftime(buffer, 32, "%Y-%m-%d %H:%M:%S", ptm); std::cout << t << "/" << buffer;
}Output: 1485498912/2017-01-27 06:35:12 Found: here
1
Standard C++ does not have any time/date functions of its own - you need to use the C localtime and related functions.
1the function "ctime()" will convert a time to a string. If you want to control the way its printed, use "strftime". However, strftime() takes an argument of "struct tm". Use "localtime()" to convert the time_t 32 bit integer to a struct tm.
The C++ way is to use stringstream.
The C way is to use snprintf() to format the number:
char buf[16]; snprintf(buf, 16, "%lu", time(NULL));Here's my formatter -- comments welcome. This q seemed like it had the most help getting me to my a so posting for anyone else who may be looking for the same.
#include <iostream>
#include "Parser.h"
#include <string>
#include <memory>
#include <ctime>
#include <chrono>
#include <iomanip>
#include <thread>
using namespace std;
string to_yyyyMMddHHmmssffffff();
string to_yyyyMMddHHmmssffffff() { using namespace std::chrono; high_resolution_clock::time_point pointInTime = high_resolution_clock::now(); std::time_t now_c = std::chrono::system_clock::to_time_t(pointInTime); microseconds micros = duration_cast<microseconds>(pointInTime.time_since_epoch()); std::size_t fractional_microseconds = micros.count() % 1'000'000; std:stringstream microstream; microstream << "00000" << fractional_microseconds; string formatted = microstream.str(); int index = formatted.length() - 6; formatted = formatted.substr(index); std::stringstream dateStream; dateStream << std::put_time(std::localtime(&now_c), "%F %T") << "." << formatted; formatted = dateStream.str(); return formatted;
}There are a myriad of ways in which you might want to format time (depending on the time zone, how you want to display it, etc.), so you can't simply implicitly convert a time_t to a string.
The C way is to use ctime or to use strftime plus either localtime or gmtime.
If you want a more C++-like way of performing the conversion, you can investigate the Boost.DateTime library.
0localtime did not work for me. I used localtime_s:
struct tm buf;
char dateString[26];
time_t time = time(nullptr);
localtime_s(&buf, &time);
asctime_s(dateString, 26, &buf);
