In linux, the C language obtains the high-precision gettimeofday function, and the high-precision gettimeofday function.

In linux, the C language obtains the high-precision gettimeofday function, and the high-precision gettimeofday function.

Preface:
Gettimeofday is used to obtain the current clock because you need to know each function or some devices perform commands during development.

1. Function Description

# Include

Int gettimeofday (struct timeval * TV, struct timezone * tz );

Note:

1. accuracy level, SubtleLevel
2. Affected by system time modification
3. The number of seconds returned is from 00:00:00, January 1, January 1, 1970.

The TV parameter is the structure used to save the time result. The tz parameter is used to save the time zone result:

The struct timeval is defined:

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Struct timeval {long int TV _sec; // number of seconds long int TV _usec; // Number of microseconds}

The obtained time is accurate Microsecond (1e-6 s) Magnitude

The struct timezone is defined:

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Struct timezone {int tz_minuteswest;/* Greenwich Mean Time difference to the west */int tz_dsttime;/* DST time correction method */}

If the timezone parameter is not used NULLYou can.
The value of tz_dsttime is as follows:

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DST_NONE/* not used */DST_USA/* us */DST_AUST/* Australia */DST_WET/* Western Europe */DST_MET/* Central Europe */DST_EET/* Eastern Europe */DST_CAN /* canada */DST_GB/* Great Britain */DST_RUM/* Romania */DST_TUR/* Turkey */DST_AUSTALT/* Australia (after 1986) */

Return Value
If the call succeeds, 0 is returned. If the call fails,-1 is returned.The error code is stored in errno.

ERRORS
EFAULT One of TV or tz pointed outside the accessible address space.
EINVAL Timezone (or something else) is invalid.
 
Ii. Instances

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1 # include <stdio. h> 2 # include <stdlib. h> 3 # include <string. h> 4 # include <sys/time. h> 5 int time_substract (struct timeval * result, struct timeval * begin, struct timeval * end) 6 {7 if (begin-> TV _sec> end-> TV _sec) return-1; 8 if (begin-> TV _sec = end-> TV _sec) & (begin-> TV _usec> end-> TV _usec) return-2; 9 result-> TV _sec = (end-> TV _sec-begin-> TV _sec); 10 result-> TV _usec = (end-> TV _usec-begin-> TV _usec ); 11 12 if (result-> TV _usec <0) 13 {14 result-> TV _sec --; 15 result-> TV _usec + = 1000000; 16} 17 return 0; 18} 19 int main (int argc, char ** argv) 20 {21 struct timeval start, stop, diff; 22 memset (& start, 0, sizeof (struct timeval )); 23 memset (& stop, 0, sizeof (struct timeval); 24 memset (& diff, 0, sizeof (struct timeval); 25 gettimeofday (& start, 0 ); 26 // do what you want to do... 27 printf ("hello world \ n"); 28 gettimeofday (& stop, 0); 29 time_substract (& diff, & start, & stop); 30 printf ("Total time: % d s, % d us \ n ", (int) diff. TV _sec, (int) diff. TV _usec); 31}

Operation Result:
Reprinted from: http://blog.chinaunix.net/uid-28458801-id-4214306.html