>>> :set -XFlexibleContexts
>>> :set -XScopedTypeVariables
>>> :set -XQuasiQuotes
>>> import Data.Function ((&))
>>> import Streamly.Unicode.String (str)
>>> import qualified Streamly.Data.Array as Array
>>> import qualified Streamly.Console.Stdio as Stdio
>>> import qualified Streamly.Data.Fold as Fold
>>> import qualified Streamly.Data.Stream.Prelude as Stream
>>> import qualified Streamly.System.Command as Command
>>> import qualified Streamly.Internal.FileSystem.Dir as Dir

>>> :{
   Command.toBytes [str|echo "hello world"|] -- Stream IO Word8
 & Command.pipeBytes [str|tr [a-z] [A-Z]|]   -- Stream IO Word8
 & Stream.fold Stdio.write                   -- IO ()
:}
HELLO WORLD

>>> :{
   Command.toBytes [str|sh "-c" "echo 'hello world' | tr [a-z] [A-Z]"|] -- Stream IO Word8
 & Stream.fold Stdio.write                                              -- IO ()
:}
HELLO WORLD

>>> :{
grep file =
   Command.toBytes [str|grep -H "pattern" #{file}|]             -- Stream IO Word8
 & Stream.handle (\(_ :: Command.ProcessFailure) -> Stream.nil) -- Stream IO Word8
 & Stream.foldMany (Fold.takeEndBy (== 10) Array.write)         -- Stream IO (Array Word8)
:}
>>> :{
pgrep =
   Dir.readFiles "."             -- Stream IO FilePath
 & Stream.parConcatMap id grep   -- Stream IO (Array Word8)
 & Stream.fold Stdio.writeChunks -- IO ()
:}