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.\"     @(#)sleep.3	8.1 (Berkeley) 6/4/93
.\" $FreeBSD: src/lib/libc/gen/sleep.3,v 1.12.2.3 2001/12/14 18:33:51 ru Exp $
.\"
.Dd February 13, 1998
.Dt SLEEP 3
.Os
.Sh NAME
.Nm sleep
.Nd suspend process execution for an interval measured in seconds
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In unistd.h
.Ft unsigned int
.Fn sleep "unsigned int seconds"
.Sh DESCRIPTION
The
.Fn sleep
function suspends execution of the calling process until either
.Fa seconds
seconds 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 seconds
seconds 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
If the
.Fn sleep
function returns because the requested time has elapsed, the value
returned will be zero.  If the
.Fn sleep
function returns due to the delivery of a signal, the value returned
will be the unslept amount (the requested time minus the time actually
slept) in seconds.
.Sh SEE ALSO
.Xr nanosleep 2 ,
.Xr usleep 3
.Sh STANDARDS
The
.Fn sleep
function conforms to
.St -p1003.1-90 .
.Sh HISTORY
A
.Fn sleep
function appeared in
.At v7 .