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.\"     @(#)usleep.3	8.1 (Berkeley) 6/4/93
.\"
.Dd June 4, 1993
.Dt USLEEP 3
.Os BSD 4.3
.Sh NAME
.Nm usleep
.Nd suspend execution for interval of microseconds
.Sh SYNOPSIS
.Fd #include <unistd.h>
.Ft int
.Fn usleep "u_int microseconds"
.Sh DESCRIPTION
The
.Fn usleep
function
suspends execution of the calling process
for
.Fa microseconds
of time.
System activity or time spent in processing the
call may lengthen the sleep slightly.
.Pp
If a timer is already running on the process its state is unaltered by
this
.Fn usleep
implementation.
If the value
.Fa microseconds
is more than or equal to the remaining clock time for the running timer,
the sleep time is set to
the remaining clock time.
.Pp
This function is implemented using
.Xr nanosleep 2
by pausing for
.Fa microseconds
of time or until any signal occurse.
.Sh RETURN VALUES
The
.Fn usleep
function returns 0 on successful completion. Otherwise, it returns -1
and sets
.Va errno
to indicate the error.
.Sh ERRORS
The
.Fn usleep
function
will fail if:
.Bl -tag -width [EINTR]
.It Bq Er EINTR
Some signal occurse.
.Sh NOTES
.Pp
A microsecond is 0.000001 seconds.
.Sh SEE ALSO
.Xr nanosleep 2 ,
.Xr setitimer 2 ,
.Xr alarm 3 ,
.Xr signal 3 ,
.Xr sleep 3 ,
.Xr ualarm 3
.Sh HISTORY
The
.Fn usleep
function appeared in 
.Bx 4.3 .