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5b2abdfb	28	.\" @(#)usleep.3 8.1 (Berkeley) 6/4/93
974e3884	29	.\" $FreeBSD$
e9ce8d39	30	.\"
5b2abdfb A	31	.Dd February 13, 1998
5b2abdfb A	32	.Dt USLEEP 3
e9ce8d39 A	33	.Os
e9ce8d39 A	34	.Sh NAME
5b2abdfb	35	.Nm usleep
ad3c9f2a	36	.Nd suspend thread execution for an interval measured in microseconds
e9ce8d39 A	37	.Sh LIBRARY
	38	.Lb libc
	39	.Sh SYNOPSIS
5b2abdfb	40	.In unistd.h
e9ce8d39	41	.Ft int
974e3884	42	.Fn usleep "useconds_t microseconds"
e9ce8d39 A	43	.Sh DESCRIPTION
e9ce8d39 A	44	The
5b2abdfb	45	.Fn usleep
ad3c9f2a	46	function suspends execution of the calling thread until either
974e3884 A	47	.Fa microseconds
	48	microseconds have elapsed or a signal is delivered to the thread and its
	49	action is to invoke a signal-catching function or to terminate the
	50	process.
	51	System activity or limitations may lengthen the sleep by an indeterminate amount.
5b2abdfb	52	.Pp
974e3884 A	53	This function is implemented using
974e3884 A	54	.Xr nanosleep 2
5b2abdfb	55	by pausing for
974e3884	56	.Fa microseconds
5b2abdfb A	57	microseconds or until a signal occurs.
5b2abdfb A	58	Consequently, in this implementation,
974e3884	59	sleeping has no effect on the state of process timers,
5b2abdfb	60	and there is no special handling for SIGALRM.
974e3884 A	61	Also, this implementation does not put a limit on the value of
	62	.Fa microseconds
	63	(other than that limited by the size of the
	64	.Ft useconds_t
	65	type); some other platforms require it to be less than one million.
	66	.Sh NOTE
	67	The
	68	.Fn usleep
	69	function is obsolescent.
	70	Use
	71	.Xr nanosleep 2
	72	instead.
e9ce8d39	73	.Sh RETURN VALUES
5b2abdfb	74	.Rv -std usleep
e9ce8d39	75	.Sh ERRORS
5b2abdfb A	76	The
	77	.Fn usleep
	78	function
e9ce8d39 A	79	will fail if:
e9ce8d39 A	80	.Bl -tag -width Er
5b2abdfb A	81	.It Bq Er EINTR
	82	A signal was delivered to the process and its
	83	action was to invoke a signal-catching function.
	84	.El
e9ce8d39	85	.Sh SEE ALSO
5b2abdfb A	86	.Xr nanosleep 2 ,
5b2abdfb A	87	.Xr sleep 3
e9ce8d39 A	88	.Sh HISTORY
e9ce8d39 A	89	The
5b2abdfb A	90	.Fn usleep
	91	function appeared in
	92	.Bx 4.3 .