Add usage examples to the README.md

README.md

@@ -109,6 +109,61 @@ giving output like this:
 
 ```
 
+## Haskell Usage
+
+The functions exported by `System.MemInfo` can be used to obtain memory usage
+of programs from haskell code:
+
+#### Example: print the program name and memory usage of single process
+
+```haskell
+import System.MemInfo (
+ readForOnePid,
+ printUsage,
+ ProcessID
+)
+
+showUsageOf :: ProcessID -> IO ()
+showUsageOf pid = do
+ orError <- readForOnePid pid
+ case orError of
+ Left err -> putStrLn $ show err
+ Right usage -> printUsage usage
+
+main :: IO ()
+main = showUsageOf 96334 -- replace with your own process ID
+```
+
+#### Example: monitor the memory of a single process continuously
+
+```haskell
+import System.MemInfo (
+ mkReportBud,
+ printUsage,
+ unfoldMemUsageAfter,
+ ProcessID
+)
+
+-- | Use 'unfoldMemUsageAfter' to periodically print out the memory usage
+monitorRamOf :: ProcessID -> IO ()
+monitorRamOf pid = do
+ budMb <- mkReportBud $ NE.singleton pid
+ case budMb of
+ Nothing -> putStrLn $ "Failed to read the system info"
+ Just bud -> do
+ let gap = 10 :: Int -- print every 10 sec
+ handleNext (Left _) = putStrLn "the process has stopped"
+ handleNext (Right ((mu, _), updated)) = do
+ putStrLn $ show mu
+ go updated
+ go x = unfoldMemUsageAfter gap x >>= handleNext
+ go bud
+
+main :: IO ()
+main = monitorRamOf 96334 -- replace with your own process ID
+```
+
+
 [hackage-deps-badge]: <https://img.shields.io/hackage-deps/v/mem-info.svg>
 [hackage-deps]: <http://packdeps.haskellers.com/feed?needle=mem-info>
 [hackage-badge]: <https://img.shields.io/hackage/v/mem-info.svg>

mem-info.cabal

@@ -15,6 +15,9 @@ description:
 
  * a library to enable core memory tracking on linux in haskell programs
 
+ See the [README](https://github.com/adetokunbo/mem-info/blob/master/README.md)
+ for further details
+
 license: BSD-3-Clause
 license-file: LICENSE
 author: Tim Emiola

src/System/MemInfo.hs

@@ -41,8 +41,14 @@ module System.MemInfo (
  dropId,
  withPid,
 
+ -- * print @MemUsage@
+ printUsage,
+ printUsage',
+
  -- * re-export
  mkReportBud,
+ ProcessID,
+ AsCmdName (..),
 ) where
 
 import Data.Bifunctor (Bifunctor (..))
@@ -125,6 +131,16 @@ printMemUsages bud showSwap onlyTotal totals = do
  reportFlaws bud showSwap onlyTotal
 
 
+-- | Print the program name and memory usage, optionally hiding the swap value.
+printUsage' :: AsCmdName a => (a, MemUsage) -> Bool -> IO ()
+printUsage' (name, mu) showSwap = Text.putStrLn $ fmtMemUsage showSwap name mu
+
+
+-- | Like printUsage, but alway shows the swap value
+printUsage :: AsCmdName a => (a, MemUsage) -> IO ()
+printUsage = flip printUsage' True
+
+
 onlyPrintTotal :: ReportBud -> Bool -> Bool -> Map k MemUsage -> IO ()
 onlyPrintTotal bud showSwap onlyTotal totals = do
  let (private, swap) = overallTotals $ Map.elems totals