I have a string that stores the no of seconds since a process started. I need to convert this string with the no of seconds to time in C++. I need to subtract this time from the current time to get the time that this process started. I am confused and I do not know how to go about it. Please could someone help me out. I am a bit new to C++
如果您使用的是较新的编译器,则可以尝试使用Boost时间库( http://www.boost.org/doc/libs/1_53_0/libs/timer/doc/index.html )或std::chrono
(建议)并希望保留在STL中。
Something like that could work:
#include <chrono>
#include <string>
using namespace std::chrono;
std::string elapsed_time_in_s = "123456";
system_clock::time_point then = system_clock::now() -
std::chrono::seconds(std::stoll(elapsed_time_in_s));
time_t then_as_time_t = system_clock::to_time_t(then);
#include <sstream>
///
std::stringstream strs(seconds_string);
unsigned int tempTime=0;
if(!(strs >> tempTime))
//error
//calculate around with tempTime
if(!(strs << tempTime)
//error
if(!(strs >> seconds_string)
//error
//new string with the current time
You can use standard <time.h>
routines ( time
, and gmtime
or localtime
).
For example:
void PrintProcessStartTimeAndDate(int numOfSeconds)
{
time_t rawtime;
struct tm* ptm;
time(&rawtime);
rawtime -= numOfSeconds;
ptm = gmtime(&rawtime); // or localtime(&rawtime);
printf("Process started at %.2d:%.2d:%.2d on %.2d/%.2d/%.2d\n",
ptm->tm_hour,ptm->tm_min,ptm->tm_sec,ptm->tm_mday,ptm->tm_mon+1,ptm->tm_year+1900);
}
Please note that gmtime
and localtime
routines are not thread-safe .
This fact is due to the pointer-to-static-structure that each one of them returns.
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