Calling a function periodically in C

Question

I want to call a function which creates files periodically on every 5 seconds in C. The function code is below which creates files.

void file_create(int time) {
        snprintf(filename, sizeof(filename),"%s_%d", "data", index);
        FILE *fp = fopen (filename, "w");
        index++;
}

file name will be data_0, data_1, data_2 and goes on on every call.

how to call the above function periodically every 5 seconds from main function if i put an infinite loop like below

while(1){
    file_create();
    Sleep(5000);
}

this is not allowing to execute the lines below the while loop.

How to achieve this by calling above function periodically without holding execution of rest of the program ?

Did you think about using a separate thread or does it have to be in the same thread? — Gerhardh, Jun 02 '20 at 13:59
Are you aware of [timerfd_create](https://man7.org/linux/man-pages/man2/timerfd_settime.2.html) ? — Gerhardh, Jun 02 '20 at 14:01
@Milag Uppercase means Windows and Microsoft's C lib plus Windows API. Glibc won't be available. — Lundin, Jun 02 '20 at 14:05
Everyone says multithreading but you can also use an event loop. Which are also large topics. Look up libuv. — Qix - MONICA WAS MISTREATED, Jun 02 '20 at 14:05
It looks like you're on Windows. Sleep(() is a [blocking call](https://en.wikipedia.org/wiki/Blocking_(computing)), which explains why you're "not executing the lines below the while loop". You definitely want to consider [Threads](https://www.bogotobogo.com/cplusplus/multithreading_win32A.php), or [Timers](https://learn.microsoft.com/en-us/windows/win32/winmsg/using-timers). [Here](https://stackoverflow.com/questions/12280224/how-to-set-a-timer-in-a-console-win32-app) is a link for using Windows Timers in a console mode all (where there's no Windows event loop). — paulsm4, Jun 02 '20 at 17:02
ALSO: you have a RESOURCE LEAK. Be sure to call `fclose()` for every time you open!!!! — paulsm4, Jun 02 '20 at 17:03

score 0 · Answer 1 · answered Jun 02 '20 at 14:00

0

You are looking for a multithread system. You have to create one task which executes the mentioned while loop and another one which executes the other parts of your current programm.

answered Jun 02 '20 at 14:00

KDD2020

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score 0 · Answer 2 · answered Jun 02 '20 at 14:01

0

You do this with multi-threading, which is a big topic by itself. I'd recommend to study how POSIX threads (pthreads) work before anything else.

In Windows, that means that the thread should waiting for a custom event "close the thread" for 5000ms. If you get the event, stop the thread. Otherwise in case of timeout, perform the periodic task. Windows uses a different thread API than POSIX.

And also different Sleep(ms) (Windows) vs sleep(s) (POSIX) functions...

answered Jun 02 '20 at 14:01

Lundin

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(Also in raw Windows API, there's a "poor man's timer" with the WM_TIMER event, which I wouldn't really recommend to use.) – Lundin Jun 02 '20 at 14:02

Calling a function periodically in C

2 Answers2