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USLEEP(3) Library Functions Manual USLEEP(3)

usleep
suspend execution for interval of microseconds

library “libc”

#include <unistd.h>

int
usleep(useconds_t microseconds);

The 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.

On successful completion, usleep() returns 0. Otherwise, it returns -1 and sets errno to indicate the error.

The usleep() function may fail if:
[]
The microseconds interval specified 1,000,000 or more microseconds.

nanosleep(2), sleep(3)

The 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.

The usleep() function appeared in 4.3BSD.
April 29, 2010 NetBSD-7.0.1