| USLEEP(3) | Library Functions Manual | USLEEP(3) | 
usleep —
#include <unistd.h>
int
  
  usleep(useconds_t
    microseconds);
usleep() function suspends execution of the calling
  process until either the number of microseconds specified by
  microseconds have elapsed or a signal is delivered to
  the calling process and its action is to invoke a signal catching function or
  to terminate the process. The suspension time may be longer than requested due
  to the scheduling of other activity by the system.
The microseconds argument must be less than 1,000,000. If the value of microseconds is 0, then the call has no effect.
usleep() returns 0. Otherwise,
  it returns -1 and sets errno to indicate the error.
usleep() function may fail if:
EINVAL]usleep() function conforms to
  X/Open Portability Guide Issue 4, Version 2
  (“XPG4.2”). It later appeared in the POSIX standard, but
  in IEEE Std 1003.1-2004 (“POSIX.1”) it
  was marked as legacy and the use of
  nanosleep(2) was recommended
  instead. The IEEE Std 1003.1-2008
  (“POSIX.1”) revision removed
  usleep() from the specification.
usleep() function appeared in
  4.3BSD.
| April 29, 2010 | NetBSD 9.4 |