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28 .\" @(#)sleep.3 8.1 (Berkeley) 6/4/93

29 .\" $FreeBSD: src/lib/libc/gen/sleep.3,v 1.17 2007/01/09 00:27:55 imp Exp $

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31 .Dd February 13, 1998

32 .Dt SLEEP 3

33 .Os

34 .Sh NAME

35 .Nm sleep

36 .Nd suspend thread execution for an interval measured in seconds

37 .Sh LIBRARY

38 .Lb libc

39 .Sh SYNOPSIS

40 .In unistd.h

41 .Ft unsigned int

42 .Fn sleep "unsigned int seconds"

43 .Sh DESCRIPTION

44 The

45 .Fn sleep

46 function suspends execution of the calling thread until either

47 .Fa seconds

48 seconds 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 thread or process.

51 System activity may lengthen the sleep by an indeterminate amount.

52 .Pp

53 This function is implemented using

54 .Xr nanosleep 2

55 by pausing for

56 .Fa seconds

57 seconds or until a signal occurs.

58 Consequently, in this implementation,

59 sleeping has no effect on the state of process timers,

60 and there is no special handling for SIGALRM.

61 .Sh RETURN VALUES

62 If the

63 .Fn sleep

64 function returns because the requested time has elapsed, the value

65 returned will be zero.

66 If the

67 .Fn sleep

68 function returns due to the delivery of a signal, the value returned

69 will be the unslept amount (the requested time minus the time actually

70 slept) in seconds.

71 .Sh SEE ALSO

72 .Xr nanosleep 2 ,

73 .Xr usleep 3

74 .Sh STANDARDS

75 The

76 .Fn sleep

77 function conforms to

78 .St -p1003.1-90 .

79 .Sh HISTORY

80 A

81 .Fn sleep

82 function appeared in

83 .At v7 .