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32.\" @(#)sleep.3 8.1 (Berkeley) 6/4/93
33.\" $FreeBSD: src/lib/libc/gen/sleep.3,v 1.16 2004/07/02 23:52:10 ru Exp $
34.\"
35.Dd February 13, 1998
36.Dt SLEEP 3
37.Os
38.Sh NAME
39.Nm sleep
40.Nd suspend thread execution for an interval measured in seconds
41.Sh LIBRARY
42.Lb libc
43.Sh SYNOPSIS
44.In unistd.h
45.Ft unsigned int
46.Fn sleep "unsigned int seconds"
47.Sh DESCRIPTION
48The
49.Fn sleep
50function suspends execution of the calling thread until either
51.Fa seconds
52seconds have elapsed or a signal is delivered to the thread and its
53action is to invoke a signal-catching function or to terminate the
54thread or process.
55System activity may lengthen the sleep by an indeterminate amount.
56.Pp
57This function is implemented using
58.Xr nanosleep 2
59by pausing for
60.Fa seconds
61seconds or until a signal occurs.
62Consequently, in this implementation,
63sleeping has no effect on the state of process timers,
64and there is no special handling for SIGALRM.
65.Sh RETURN VALUES
66If the
67.Fn sleep
68function returns because the requested time has elapsed, the value
69returned will be zero.
70If the
71.Fn sleep
72function returns due to the delivery of a signal, the value returned
73will be the unslept amount (the requested time minus the time actually
74slept) in seconds.
75.Sh SEE ALSO
76.Xr nanosleep 2 ,
77.Xr usleep 3
78.Sh STANDARDS
79The
80.Fn sleep
81function conforms to
82.St -p1003.1-90 .
83.Sh HISTORY
84A
85.Fn sleep
86function appeared in
87.At v7 .