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

29 .\" $FreeBSD$

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31 .Dd February 13, 1998

32 .Dt USLEEP 3

33 .Os

34 .Sh NAME

35 .Nm usleep

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

37 .Sh LIBRARY

38 .Lb libc

39 .Sh SYNOPSIS

40 .In unistd.h

41 .Ft int

42 .Fn usleep "useconds_t microseconds"

43 .Sh DESCRIPTION

44 The

45 .Fn usleep

46 function suspends execution of the calling thread until either

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.

52 .Pp

53 This function is implemented using

54 .Xr nanosleep 2

55 by pausing for

56 .Fa microseconds

57 microseconds 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 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.

73 .Sh RETURN VALUES

74 .Rv -std usleep

75 .Sh ERRORS

76 The

77 .Fn usleep

78 function

79 will fail if:

80 .Bl -tag -width Er

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

85 .Sh SEE ALSO

86 .Xr nanosleep 2 ,

87 .Xr sleep 3

88 .Sh HISTORY

89 The

90 .Fn usleep

91 function appeared in

92 .Bx 4.3 .