Question

I saw in usleep man that :

EINVAL
usec is not smaller than 1000000. (On systems where that is considered an error.) 

So i wonder if its ok to use usleep in Ubuntu with value greater than 1000000 and if not (or in case that i want to support other platforms ) what is the alternative when i need sleep for 2.2 sec (for example) .

Thank you.

Answer 1

One alternative is to trust the documentation and implement it using a loop just to be safe:

#define USLEEP_MAX (1000000 - 1)

void long_sleep(unsigned long micros)
{
  while(micros > 0)
  {
    const unsigned long chunk = micros > USLEEP_MAX ? USLEEP_MAX : micros;
    usleep(chunk);
    micros -= chunk;
  }
}

You should also inspect the return value of usleep(), I omitted that for brevity.

In production, you can have fun with Autoconf and friends to detect the proper USLEEP_MAX at compile-time, and even switch to a plain wrapper if the local system doesn’t have a limit for the argument. Hours of fun can be had.