Get interval between 2 operations using ctime?

Question

I am interested in showing the execution time for a program in C, at diverse points, using ctime. I have tried something like that, but it must not be right...

int main() {

    time_t tm1, tm2;
    tm1 = time(NULL);
    sleep(2);
    tm2 = ctime(tm1);

    printf("%d\n", tm2-tm1);
    return 0;
}

Do you have any suggestion or a proper example? Thanks in advance

It depends on in what granulity you want to get result. If seconds so its ok to get time in the beginning and in the end of main via `time()`. — Mihran Hovsepyan, Apr 30 '11 at 21:03
yes, preferably in seconds! but my code is not functional :( — Madrugada, Apr 30 '11 at 21:04
You shoud take `time(NULL)` in both cases. It returns current time. — Mihran Hovsepyan, Apr 30 '11 at 21:07

score 5 · Accepted Answer · answered Apr 30 '11 at 21:04

5

ctime() returns a string representation of the time passed into it.

If you want a simple elapsed time, just:

    time_t t1, t2;
    t1 = time(0);
    sleep(2);
    t2 = time(0);

    printf("Elapsed: %d\n", t2 - t1);

See man ctime and man 2 time.

answered Apr 30 '11 at 21:04

unpythonic

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2

`difftime(t2, t1)` (which is a `double`) is the portable way to do it. – Alok Singhal Apr 30 '11 at 22:46

score 2 · Answer 2 · answered Apr 30 '11 at 22:35

You can use the time function to get the current time and the difftime function to compute the difference, in seconds, between two times (error handling omitted):

time_t t0, t1;
t0 = time(NULL);
foo();
t1 = time(NULL);
printf("foo() took %f seconds.\n", difftime(t1, t0));

However, time_t is intended for measuring calendar times. The time function typically has a one-second interval. If this is too coarse, you can try using clock_t and the clock function (error handling omitted again):

clock_t t0, t1;
t0 = clock();
foo();
t1 = clock();
printf("foo() took %f seconds.\n", (double)((t1 - t0) / CLOCKS_PER_SEC));

Get interval between 2 operations using ctime?

2 Answers2