Sleeping for milliseconds on Windows, Linux, Solaris, HP-UX, IBM AIX, Vxworks, Wind River Linux?

Question

I have to write a C program which has to sleep for milliseconds, which has to run on various platforms like Windows, Linux, Solaris, HP-UX, IBM AIX, Vxworks, and Windriver L

Answer 1

I note that usleep is obsolescent but its a lot simpler than nanosleep. So I used it when I needed an enhanced sleep that would allow easy adjustment from seconds while debugging my scripts to milliseconds or zero for production.

This snooze function combines the advantages of sleep & usleep so that you can enter an int or float for your desired delay and 0.1 will sleep a 10th of a second while 3 will sleep for 3 seconds. 3.5 seconds is treated as 3 seconds.

Tested on Linux Mint 18.3 (Ubuntu 16.04.9) as C and C++ with gcc 5.4.0.

#include 

void snooze(double t) {(t > 1.0) ? sleep(t) : usleep(t*1000000);}

snooze(0.01);  // call function to sleep for 10ms

---

For completeness, this is a nanosleep version. It's potentially more accurate than the usleep version and isn't threatened by obsolescence.

#include 
#include 

void snooze(double t) {
    struct timespec req = {t, fmod(t, 1.0) * 1E9};
    nanosleep(&req, NULL);
}

// struct timespec req = {t, fmod(t, 1.0) * 1E9};
//  is equivalent to:
// struct timespec req = {0};
// req.tv_sec = t;
// req.tv_nsec = fmod(t, 1.0) * 1000000000L;

// NULL as value for *rem so no resumption after signal interrupts

snooze(1.99);  // call for delay of 1.99 seconds

---

As suggested by @alk, the following versions return the called sleep function's error should one occur or 0 if successful. Defining the structure rem(aining) also permits resumption after a signal interrupt.

int snooze(double t) {
    return (t > 1.0) ? sleep(t) : usleep(t*1000000);
}

int snooze(double t) {
    struct timespec req = {t, fmod(t, 1.0) * 1E9};
    struct timespec rem = {0, 0.0};
    return nanosleep(&req, &rem);
}