difftime
Defined in header <time.h>
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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.
#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
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