freebsd-dev/lib/libc/gen/usleep.3

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.\" Copyright (c) 1986, 1991, 1993
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.\" @(#)usleep.3 8.1 (Berkeley) 6/4/93
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.\" $FreeBSD$
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.\"
.Dd February 13, 1998
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.Dt USLEEP 3
.Os
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.Sh NAME
.Nm usleep
.Nd suspend process execution for an interval measured in microseconds
.Sh LIBRARY
.Lb libc
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.Sh SYNOPSIS
.In unistd.h
.Ft int
.Fn usleep "useconds_t microseconds"
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.Sh DESCRIPTION
The
.Fn usleep
function suspends execution of the calling process until either
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.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.
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.Pp
This function is implemented using
.Xr nanosleep 2
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by pausing for
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.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.
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.El
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.Sh SEE ALSO
.Xr nanosleep 2 ,
.Xr sleep 3
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.Sh HISTORY
The
.Fn usleep
function appeared in
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.Bx 4.3 .