difftime

 

C

Language

Standard Library

Type support

Dynamic memory management

Error handling

Program utilities

Date and time utilities

Strings library

Algorithms

Numerics

Input/output support

Localization support

Thread support (C11)

Atomic operations (C11)

 

Date and time utilities

Functions

Time manipulation

difftime

time

clock

Format conversions

asctime

ctime

strftime

wcsftime

gmtime

localtime

mktime

Constants

CLOCKS_PER_SEC

Types

tm

time_t

clock_t

 

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()
{
    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:

1937968.000000 seconds have passed since the beginning of the month.