[英]Timestamps for embedded system
I would like to add timestamps to sensor measurements on an embedded system (Raspberry Pi A+ running ArchLinux). 我想在嵌入式系统(运行ArchLinux的Raspberry Pi A +)上为传感器测量添加时间戳。 I've found time
from time.h
but it gives me "second" resolution and I would need at least "milliseconds". 我从time.h
找到了time
,但是它给了我“秒”的分辨率,我至少需要“毫秒”。 The system would run for a few hours, I'm not concerned about long duration drifts. 该系统将运行几个小时,我不担心长时间漂移。
How could I get that in C++? 我怎么能用C ++做到这一点?
If you have C++11
you can use the <chrono>
and <ctime>
library like this: 如果您具有C++11
,则可以使用<chrono>
和<ctime>
库,如下所示:
#include <ctime>
#include <string>
#include <chrono>
#include <sstream>
#include <iomanip>
#include <iostream>
// use strftime to format time_t into a "date time"
std::string date_time(std::time_t posix)
{
char buf[20]; // big enough for 2015-07-08 10:06:51\0
std::tm tp = *std::localtime(&posix);
return {buf, std::strftime(buf, sizeof(buf), "%F %T", &tp)};
}
std::string stamp()
{
using namespace std;
using namespace std::chrono;
// get absolute wall time
auto now = system_clock::now();
// find the number of milliseconds
auto ms = duration_cast<milliseconds>(now.time_since_epoch()) % 1000;
// build output string
std::ostringstream oss;
oss.fill('0');
// convert absolute time to time_t seconds
// and convert to "date time"
oss << date_time(system_clock::to_time_t(now));
oss << '.' << setw(3) << ms.count();
return oss.str();
}
int main()
{
std::cout << stamp() << '\n';
}
Output: 输出:
2015-07-08 10:13:29.930
Note: 注意:
If you want higher resolution you can use microseconds
like this: 如果需要更高的分辨率,可以使用以下microseconds
:
std::string stamp()
{
using namespace std;
using namespace std::chrono;
auto now = system_clock::now();
// use microseconds % 1000000 now
auto us = duration_cast<microseconds>(now.time_since_epoch()) % 1000000;
std::ostringstream oss;
oss.fill('0');
oss << date_time(system_clock::to_time_t(now));
oss << '.' << setw(6) << us.count();
return oss.str();
}
Output: 输出:
2015-07-08 10:20:39.454163
C ++ 11 chrono头文件中有很多功能,请参考此给定链接
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