look for sysctl in some common sbin locations when it's not in PATH

Utility/INotify.hs

@@ -164,10 +164,11 @@ tooManyWatches hook dir = do
 			]
 
 querySysctl :: Read a => [CommandParam] -> IO (Maybe a)
-querySysctl ps = do
-	v <- catchMaybeIO $ readProcess "sysctl" (toCommand ps)
-	case v of
-		Nothing -> return Nothing
-		Just s -> return $ parsesysctl s
+querySysctl ps = getM go ["sysctl", "/sbin/sysctl", "/usr/sbin/sysctl"]
 	where
+		go p = do
+			v <- catchMaybeIO $ readProcess p (toCommand ps)
+			case v of
+				Nothing -> return Nothing
+				Just s -> return $ parsesysctl s
 		parsesysctl s = readish =<< lastMaybe (words s)

Utility/Monad.hs

@@ -16,6 +16,12 @@ firstM :: Monad m => (a -> m Bool) -> [a] -> m (Maybe a)
 firstM _ [] = return Nothing
 firstM p (x:xs) = ifM (p x) (return $ Just x , firstM p xs)
 
+{- Runs the action on values from the list until it succeeds, returning
+ - its result. -}
+getM :: Monad m => (a -> m (Maybe b)) -> [a] -> m (Maybe b)
+getM _ [] = return Nothing
+getM p (x:xs) = maybe (getM p xs) (return . Just) =<< p x
+
 {- Returns true if any value in the list satisfies the predicate,
  - stopping once one is found. -}
 anyM :: Monad m => (a -> m Bool) -> [a] -> m Bool