$OpenBSD: usleep.3,v 1.19 2013/06/05 03:39:22 tedu Exp $

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.Dd $Mdocdate: October 16 2012 $ .Dt USLEEP 3 .Os .Sh NAME .Nm usleep .Nd suspend process execution for interval measured in microseconds .Sh SYNOPSIS n unistd.h .Ft int .Fn usleep "useconds_t microseconds" .Sh DESCRIPTION f -symbolic This interface is obsoleted by .Xr nanosleep 2 . .Ef

p The .Fn usleep function suspends execution of the calling process until either .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. The suspension time may be longer than requested due to the scheduling of other activity by the system.

p This function is implemented using .Xr nanosleep 2 by pausing for .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 .Dv SIGALRM . .Sh RETURN VALUES .Rv -std usleep .Sh ERRORS The .Fn usleep function will fail if: l -tag -width Er t Bq Er EINTR A signal was delivered to the process and its action was to invoke a signal-catching function. .El .Sh NOTES A microsecond is 0.000001 seconds. .Sh SEE ALSO .Xr sleep 1 , .Xr nanosleep 2 , .Xr sleep 3 .Sh STANDARDS The .Fn usleep function conforms to .St -xpg4.2 . .Sh HISTORY The .Fn usleep function appeared in x 4.3 . .Sh CAVEATS Some implementations of .Fn usleep return an error if .Fa microseconds is greater than or equal to 1,000,000. Portable applications should be written with this limitation in mind.