0 Indicates success. The requested time has
elapsed.
-1 Indicates failure. The function call was
unsuccessful or was interrupted by a signal;
errno is set to one of the following values:
o EINTR - The nanosleep function was
interrupted by a signal.
o EINVAL - The rqtp argument specified a
nanosecond value less than 0 or greater
than or equal to 1 billion.