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.\" Copyright (c) 1986, 1991, 1993
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.\" @(#)usleep.3 8.1 (Berkeley) 6/4/93
.\" $FreeBSD$
.\"
.Dd February 13, 1998
.Dt USLEEP 3
.Os
.Sh NAME
.Nm usleep
.Nd suspend process execution for an interval measured in microseconds
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In unistd.h
.Ft int
.Fn usleep "unsigned int microseconds"
.Sh DESCRIPTION
The
.Fn usleep
function suspends execution of the calling process until either
.Fa microseconds
microseconds have elapsed or a signal is delivered to the process and its
action is to invoke a signal-catching function or to terminate the
process.
System activity may lengthen the sleep by an indeterminate amount.
.Pp
This function is implemented using
.Xr nanosleep 2
by pausing for
.Fa microseconds
microseconds or until a signal occurs.
Consequently, in this implementation,
sleeping has no effect on the state of process timers,
and there is no special handling for SIGALRM.
.Sh RETURN VALUES
.Rv -std usleep
.Sh ERRORS
The
.Fn usleep
function
will fail if:
.Bl -tag -width Er
.It Bq Er EINTR
A signal was delivered to the process and its
action was to invoke a signal-catching function.
.El
.Sh SEE ALSO
.Xr nanosleep 2 ,
.Xr sleep 3
.Sh HISTORY
The
.Fn usleep
function appeared in
.Bx 4.3 .
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