gcc (GCC) 4.6.3
c89

Hello,

I am trying to use usleep. However, I keep getting the following warning:

implicit declaration of function usleep

I have included the unistd.h header file.

The man pages mentions something about this. But I am not sure I understand by it:

   usleep():
       Since glibc 2.12:
           _BSD_SOURCE ||
               (_XOPEN_SOURCE >= 500 ||
                   _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED) &&
               !(_POSIX_C_SOURCE >= 200809L || _XOPEN_SOURCE >= 700)
       Before glibc 2.12:
           _BSD_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED

But not sure what I a to do with the above?

Many thanks for any suggestions,