How to read the time in C + +

"Summary" This article describes the method of obtaining calendar time under C/s + +, which is different from the Java language, and it seems that there is not a one-time method to obtain the readability of the HH:MM:SS, the common three-step approach is introduced, and the time acquisition of Nanosecond and Microsecond is introduced in this paper.

1, for C language, need to include the header file:

1 #include <sys/time.h>

2, get the date need to get the calendar time, that is, January 1, 1970 00:00:00 to date the number of seconds, in the Linux system for the time_t type, which is equivalent to 1 long type.

Then the time_t is converted into a TM structure, and the TM structure includes data such as minutes, seconds, hours, days, months, and years.

Use Clock_gettime to get the calendar time code as follows:

#include <iostream>#include<sys/time.h>using namespacestd;intMain () {structTimespec tsp; Clock_gettime (Clock_realtime,&TSP); structTM *TMV = gmtime (&tsp.tv_sec); cout<<"Calendar Time:"<<tsp.tv_sec<<Endl; cout<<"seconds in UTC:"<<tmv->tm_sec<<Endl; cout<<"when in UTC:"<<tmv->tm_hour<<Endl;}

Results:
Calendar Time: 1475654852
Seconds in UTC: 32
Time in UTC: 8

There are three ways to get calendar time:

time_t time (time_t *calptr); // accurate to seconds int struct timespec *tsp); // Accurate to nanosecond int gettimeofday (structvoid *restrict tzp); // accurate to microseconds

3, if you need to obtain milliseconds and microseconds, you can not use the above time_t and TM data, Timespec and TIMEVAL two structures are available in C/s + +, where Timespec includes time_t type and nanosecond, Timeval includes time_ Type T and microsecond type.

#include <iostream>#include<sys/time.h>using namespacestd;intMain () {structTimespec tsp; structTimeval TVL; Clock_gettime (Clock_realtime,&TSP); cout<<"type of time_t in Timespec (precision seconds):"<<tsp.tv_sec<<Endl; cout<<"type of nanosecond in Timespec:"<<tsp.tv_nsec<<Endl; Gettimeofday (&tvl,null); cout<<"type of time_t in Timeval (precision seconds)"<<tvl.tv_sec<<Endl; cout<<"types of microseconds in Timeval:"<<tvl.tv_usec<<Endl;}

Results:
time_t type in Timespec (precision seconds): 1475654893
Nanosecond type in Timespec: 644958756
time_t type in Timeval (precision seconds) 1475654893
Type of microsecond in Timeval: 645036

4. Display the current date in an easy-to-read manner, and C + + provides the Strptime function to convert the time_t to a different type of time format, but it's more complex, and here's an example:

#include <iostream>#include<sys/time.h>using namespacestd;intMain () {structTimespec tsp; Clock_gettime (Clock_realtime,&TSP); Charbuf[ -]; structTM *tmp = localtime (&tsp.tv_sec); if(Strftime (BUF, -,"Date and time:%y-%m-%d%h:%m:%s", tmp) = =0) {cout<<"buffer length is too small\n"; }    Else{cout<<buf<<Endl; }} KnotFruit:
Date and time:2016-10-05 16:02:45

5. The relationship between time data type and time function

How to read the time in C + +