I'm trying to know the timestamp when I receive a message.
I should check if it has been N seconds of receiving the last message.
I'm using time_t.
I take the current time like this: time (& myTime);
how can I check if they spent more than N seconds?
Is there a way to know the number of seconds (timestamp) of a total time_t?
You ask the "number of seconds" of a time_t. This would be absolute time. You'd want probably then want to format it using localtime() or some such function in hour/minute/second, day/month/year form.
If you want to know the time since a previous event, you should simply save the time_t from that event and then use a statement like if (difftime(thisevent_time, lastevent_time) > max_seconds) to handle it.
Related
I'm trying to get the Start Time of a running process on Windows. I did some searching and a couple of people suggested getting the Creation Time of a process with GetProcessTimes() but this doesn't seem to return accurate information. After converting the time to systemtime, it seems to return 23 for the hour instead of the correct time. How do I get the correct time? Surely there has to be a way if Process Explorer can do it.
// Returns the wrong time
SYSTEMTIME ftime;
FILETIME creationTime;
GetProcessTimes(hProcess, &creationTime, &exitTime, &kernelTime, &userTime);
FileTimeToSystemTime(&creationTime, &ftime);
FileTimeToSystemTime() gets the time in UTC time. 23 is the right answer for another 10 minutes :)
You can use SystemTimeToTzSpecificLocalTime() to convert the UTC time to the local time zone (by passing NULL as the first parameter), or to any other time zone you want.
I'm writing a C++ DLL which will be accessed using MATLAB's loadlibrary. I need a specific function to return the current time in milliseconds precision, and parse it correctly in matlab. Specifically i'll need to extract the year, month, day, hours, minutes, seconds and milliseconds.
I currently have something like
long long time_since_epoch()
{
return std::chrono::system_clock::now().time_since_epoch().count();
}
which MATLAB calls using t = calllib('myDLL', 'time_since_epoch');.
Then I tried parsing it using dt = datetime(t, 'convertfrom', 'epochtime');, which didn't work.
But, I compared it with the time given from posixtime(datetime) and found out I'm getting a correct answer by using dt = datetime(t / 10000000, 'convertfrom', 'epochtime');, which is very odd.
I don't fully understand what's going on here, and I somehow lost the milliseconds in the process.
Your system_clock is not counting milliseconds, it is counting something finer than a millisecond. Exactly what isn't important because you can specifically ask for the count in milliseconds:
long long time_since_epoch()
{
using namespace std::chrono;
return time_point_cast<milliseconds>(system_clock::now()).time_since_epoch().count();
}
I have a counter "numberOrders" and i want to reset it everyday at midnight, to know how many orders I get in one day, what I have right now is this:
val system = akka.actor.ActorSystem("system")
system.scheduler.schedule(86400000 milliseconds, 0 milliseconds){(numberOrders = 0)}
This piece of code is inside a def which is called every time i get a new order, so want it does is: reset numberOrders after 24hours from the first order or from every order, I'm not really sure if every time there's a new order is going to reset after 24 hours, which is not what I want. I want to rest the variable everyday at midnight, any idea? Thanks!
To further increase pushy's answer. Since you might not always be sure when the site started and if you want to be exactly sure it runs at midnight you can do the following
val system = akka.actor.ActorSystem("system")
val wait = (24 hours).toMillis - System.currentTimeMillis
system.scheduler.schedule(Duration.apply(wait, MILLISECONDS), 24 hours, orderActor, ResetCounterMessage)
Might not be the tidiest of solutions but it does the job.
As schedule supports repeated executions, you could just set the interval parameter to 24 hours, the initial delay to the amount of time between now and midnight, and initiate the code at startup. You seem to be creating a new actorSystem every time you get an order right now, that does not seem quite right, and you would be rid of that as well.
Also I would suggest using the schedule method which sends messages to actors instead. This way the actor that processes the order could keep count, and if it receives a ResetCounter message it would simply reset the counter. You could simply write:
system.scheduler.schedule(x seconds, 24 hours, orderActor, ResetCounterMessage)
when you start up your actor system initially, and be done with it.
I am trying to retrieve Current Time in milliseconds using boost library.. Below is my code which I am using to get the current time in milliseconds.
boost::posix_time::ptime time = boost::posix_time::microsec_clock::local_time();
boost::posix_time::time_duration duration( time.time_of_day() );
std::cout << duration.total_milliseconds() << std::endl;
uint64_t timestampInMilliseconds = duration.total_milliseconds() // will this work or not?
std::cout << timestampInMilliseconds << std::endl;
But this prints out in 10 digit which is like 17227676.. I am running my code on my ubuntu machine.. And I believe it is always 13 digit long value? Isn't so?
After computing the timestamp in milliseconds, I need to use below formula on that -
int end = (timestampInMilliseconds / (60 * 60 * 1000 * 24)) % 14
But somehow I am not sure whether timestampInMilliseconds which I am getting is right or not?
First of all should I be using boost::posix or not? I am assuming there might be some better way.. I am running code on my ubuntu machine..
Update:-
As this piece of bash script prints out timestampInMilliseconds which is of 13 digit..
date +%s%N | cut -b1-13
The problem here is that you use time_of_day() which returns (from this reference)
Get the time offset in the day.
So from the value you provided in the question I can deduce that you ran this program at 4:47 am.
Instead you might want to use e.g. the to_tm() to get a struct tm and construct your time in milliseconds from there.
Also note that the %s format to the date command (and the strftime function) is the number of seconds since the epoch, not the number of milliseconds.
If you look at the tm structure, you will see that it has the number of years (since 1900, so subtract 70 here), days into the year, and then hours,, minutes and seconds into the day. All these can be used to calculate the time in seconds easily.
And that in seconds is the problem here. If you look at e.g. the POSIX time function you see that
shall return the value of time in seconds since the Epoch
If you want an accurate millisecond resolution you simply can't use the ptime (where the p stands for POSIX). If you want millisecond resolution you either have to use e.g. system functions that returns the time in higher resolutions (like gettimeofday), or you can see e.g. this old SO answer.
How can you obtain the system clock's current time of day (in milliseconds) in C++? This is a windows specific app.
The easiest (and most direct) way is to call GetSystemTimeAsFileTime(), which returns a FILETIME, a struct which stores the 64-bit number of 100-nanosecond intervals since midnight Jan 1, 1601.
At least at the time of Windows NT 3.1, 3.51, and 4.01, the GetSystemTimeAsFileTime() API was the fastest user-mode API able to retrieve the current time. It also offers the advantage (compared with GetSystemTime() -> SystemTimeToFileTime()) of being a single API call, that under normal circumstances cannot fail.
To convert a FILETIME ft_now; to a 64-bit integer named ll_now, use the following:
ll_now = (LONGLONG)ft_now.dwLowDateTime + ((LONGLONG)(ft_now.dwHighDateTime) << 32LL);
You can then divide by the number of 100-nanosecond intervals in a millisecond (10,000 of those) and you have milliseconds since the Win32 epoch.
To convert to the Unix epoch, subtract 116444736000000000LL to reach Jan 1, 1970.
You mentioned a desire to find the number of milliseconds into the current day. Because the Win32 epoch begins at a midnight, the number of milliseconds passed so far today can be calculated from the filetime with a modulus operation. Specifically, because there are 24 hours/day * 60 minutes/hour * 60 seconds/minute * 1000 milliseconds/second = 86,400,000 milliseconds/day, you could user the modulus of the system time in milliseconds modulus 86400000LL.
For a different application, one might not want to use the modulus. Especially if one is calculating elapsed times, one might have difficulties due to wrap-around at midnight. These difficulties are solvable, the best example I am aware is Linus Torvald's line in the Linux kernel which handles counter wrap around.
Keep in mind that the system time is returned as a UTC time (both in the case of GetSystemTimeAsFileTime() and simply GetSystemTime()). If you require the local time as configured by the Administrator, then you could use GetLocalTime().
To get the time expressed as UTC, use GetSystemTime in the Win32 API.
SYSTEMTIME st;
GetSystemTime(&st);
SYSTEMTIME is documented as having these relevant members:
WORD wYear;
WORD wMonth;
WORD wDayOfWeek;
WORD wDay;
WORD wHour;
WORD wMinute;
WORD wSecond;
WORD wMilliseconds;
As shf301 helpfully points out below, GetLocalTime (with the same prototype) will yield a time corrected to the user's current timezone.
You have a few good answers here, depending on what you're after. If you're looking for just time of day, my answer is the best approach -- if you need solid dates for arithmetic, consider Alex's. There's a lot of ways to skin the time cat on Windows, and some of them are more accurate than others (and nobody has mentioned QueryPerformanceCounter yet).
A cut-to-the-chase example of Jed's answer above:
const std::string currentDateTime() {
SYSTEMTIME st, lt;
GetSystemTime(&st);
char currentTime[84] = "";
sprintf(currentTime,"%d/%d/%d %d:%d:%d %d",st.wDay,st.wMonth,st.wYear, st.wHour, st.wMinute, st.wSecond , st.wMilliseconds);
return string(currentTime); }
Use GetSystemTime, first; then, if you need that, you can call SystemTimeToFileTime on the SYSTEMTIME structure that the former fills for you. A FILETIME is a 64-bit count of 100-nanosecs intervals since an epoch, and so more suitable for arithmetic; a SYSTEMTIME is a structure with all the expected fields (year, month, day, hour, etc, down to milliseconds). If you want to know "how many milliseconds have elapsed since midnight", for example, subtracting two FILETIME structures (one for the current time, one obtained by converting the same SYSTEMTIME after zeroing out the appropriate fields) and dividing by the appropriate power of ten is probably the simplest available approach.
Depending on the needs of your application there are six common options. This Dr Dobbs Journal article will give you all the information (and more) you need on choosing the best one.
In your specific case, from this article:
GetSystemTime() retrieves the current
system time and instantiates a
SYSTEMTIME structure, which is
composed of a number of separate
fields including year, month, day,
hours, minutes, seconds, and
milliseconds.
Here is some code that works in Windows which I've used in a Open Watcom C project. It should work in C++ It returns seconds (not milliseconds) using _dos_gettime or gettime
double seconds(void)
{
#ifdef __WATCOMC__
struct dostime_t t;
_dos_gettime(&t);
return ((double)t.hour * 3600 + (double)t.minute * 60 + (double)t.second + (double)t.hsecond * 0.01);
#else
struct time t;
gettime(&t);
return ((double)t.ti_hour * 3600 + (double)t.ti_min * 60 + (double)t.ti_sec + (double)t.ti_hund * 0.01);
#endif
}
While it's not what the question asks, it's worth considering why you want this info.
If all you want to do is keep track of how long something takes to calculate or the time past since the last user interaction, consider using the uptime (milliseconds since boot), which is much simpler to get: GetTickCount() or GetTickCount64(). This is all I wanted to do but I went down the epoch rabbit hole first because that's how you do it under unix.