difftime

< c‎ | chrono
 
C
 
Date and time utilities
Functions
Time manipulation
difftime
(C11)
Format conversions
(C11)
(C11)
(C95)
(C11)
(C11)
Constants
Types
(C11)
 
Defined in header <time.h>
double difftime( time_t time_end, time_t time_beg );

Computes difference between two calendar times as time_t objects (time_end - time_beg) in seconds. If time_end refers to time point before time_beg then the result is negative.

Parameters

time_beg, time_end - times to compare

Return value

Difference between two times in seconds.

Notes

On POSIX systems, time_t is measured in seconds, and difftime is equivalent to arithmetic subtraction, but C and C++ allow fractional units for time_t.

Example

The following program computes the number of seconds that have passed since the beginning of the month.

Run this code
#include <stdio.h>
#include <time.h>
 
int main(void)
{
    time_t now;
    time(&now);
 
    struct tm beg;
    beg = *localtime(&now);
 
    // set beg to the beginning of the month
    beg.tm_hour = 0;
    beg.tm_min = 0;
    beg.tm_sec = 0;
    beg.tm_mday = 1;
 
    double seconds = difftime(now, mktime(&beg));
 
    printf("%.f seconds have passed since the beginning of the month.\n", seconds);
 
    return 0;
}

Output: 

1937968 seconds have passed since the beginning of the month.

References

  • C11 standard (ISO/IEC 9899:2011):
  • 7.27.2.2 The difftime function (p: 390)
  • C99 standard (ISO/IEC 9899:1999):
  • 7.23.2.2 The difftime function (p: 339)
  • C89/C90 standard (ISO/IEC 9899:1990):
  • 4.12.2.2 The difftime function

See also