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.Dd $Mdocdate: July 26 2019 $ .Dt UALARM 3 .Os .Sh NAME .Nm ualarm .Nd schedule high resolution SIGALRM delivery .Sh SYNOPSIS n unistd.h .Ft useconds_t .Fn ualarm "useconds_t microseconds" "useconds_t interval" .Sh DESCRIPTION f -symbolic This is a simplified interface to .Xr setitimer 2 . .Ef
p The .Fn ualarm function schedules the .Dv SIGALRM signal for delivery to the calling process after at least the given number of .Fa microseconds have elapsed. If .Fa interval is non-zero, the .Dv SIGALRM signal is scheduled for redelivery to the calling process every .Fa interval microseconds thereafter.
p If an alarm is already pending, an additional call to .Fn ualarm supersedes the prior call.
p If .Fa microseconds is zero, any pending alarm is cancelled and the value of .Fa interval is ignored. .Sh RETURN VALUES The .Fn ualarm function returns the number of microseconds remaining until the next alarm is scheduled for delivery, or zero if no alarm is pending. .Sh SEE ALSO .Xr setitimer 2 , .Xr sigaction 2 , .Xr sigsuspend 2 , .Xr alarm 3 , .Xr signal 3 , .Xr sleep 3 , .Xr usleep 3 .Sh STANDARDS The .Fn ualarm function conforms to .St -xpg4.2 . .Sh HISTORY The .Fn ualarm function first appeared in x 4.3 . .Sh CAVEATS The .Fn ualarm function is implemented with the per-process .Dv ITIMER_REAL timer described in .Xr setitimer 2 . Use of both .Fn ualarm and .Xr setitimer 2 in the same program may yield confusing behavior.