This is what I have so far:
type Pid = FilePath type Uid = String
type PsData = Map String Uid type PsChildren = Map Pid PsInfo
data PsInfo = PsInfo PsData PsChildren type PsMap = Map Pid PsInfo type PsTree = Map Pid PsInfo
parent :: PsData -> Pid parent psData = fromJust $ Map.lookup "PPid" psData
getProcInfo :: PsData -> String -> IO PsData getProcInfo psData line = do case matchRegex (mkRegex "^([a-z]+):[[:space:]]+(.*)$") line of Nothing -> return (psData) Just [key, value] -> return (Map.insert key value psData)
procInfo :: Pid -> IO PsInfo procInfo pid = do procData <- readFile $ "/proc/" ++ pid ++ "/status" psData <- foldM getProcInfo Map.empty (lines procData) let [rUid, eUid, _] = words $ fromJust (Map.lookup "Uid" psData) let [rGid, eGid, _] = words $ fromJust (Map.lookup "Gid" psData) let uids = Map.fromList [("RUid", rUid), ("EUid", eUid), ("RGid", rGid), ("EGid", eGid)] let psData' = Map.union psData uids return (PsInfo psData' Map.empty)
I tried this for insertProc, but it obviously doesn't work... what would be the correct way to do this?
insertProc :: Pid -> StateT PsMap IO PsInfo insertProc pid = do proc <- procInfo pid -- XXX this is obviously wrong... psMap <- get put (Map.insert pid proc psMap) return (proc)
A second question: is it possible to make getProcInfo's type to be PsData -> String -> PsData and use some operation similar to lift so that it can be used with foldM, instead of making its return type to be IO PsData explicitely?
Yes, and in fact, you don't even need foldM. The only thing that actually uses IO is the readFile, so ideally you should just have a small function that just does the readFile and then processes the result using some (pure) functions. Something like this:
procInfo :: Pid -> IO PsInfo procInfo pid = do procData <- readFile $ "/proc/" ++ pid ++ "/status" return $ processData procData
processData :: String -> PsInfo ... and so on ...
and so on. Now instead of using foldM you can just use foldr. IO is a cancer, best to keep it confined to as little of your program as possible! =) -Brent