Package Info


Simple, composable, and easy-to-use stream I/O



The io-streams library contains simple and easy-to-use primitives for I/O using streams. Most users will want to import the top-level convenience module "System.IO.Streams", which re-exports most of the library:

' import System.IO.Streams (InputStream, OutputStream) import qualified System.IO.Streams as Streams '

For first-time users, 'io-streams' comes with an included tutorial, which can be found in the "System.IO.Streams.Tutorial" module.


The 'io-streams' user API has two basic types: 'InputStream a' and 'OutputStream a', and three fundamental I/O primitives:

' -- read an item from an input stream :: InputStream a -> IO (Maybe a)

-- push an item back to an input stream Streams.unRead :: a -> InputStream a -> IO ()

-- write to an output stream Streams.write :: Maybe a -> OutputStream a -> IO () '

Streams can be transformed by composition and hooked together with provided combinators:

' ghci> Streams.fromList [1,2,3::Int] >>= (*10) >>= Streams.toList [10,20,30] '

Stream composition leaves the original stream accessible:

' ghci> input <- Streams.fromByteString "long string" ghci> wrapped <- Streams.takeBytes 4 input ghci> wrapped Just "long" ghci> wrapped Nothing ghci> input Just " string" '

Simple types and operations in the IO monad mean straightforward and simple exception handling and resource cleanup using Haskell standard library facilities like 'Control.Exception.bracket'.

'io-streams' comes with:

  • functions to use files, handles, concurrent channels, sockets, lists,

vectors, and more as streams.

  • a variety of combinators for wrapping and transforming streams, including

compression and decompression using zlib, controlling precisely how many bytes are read from or written to a stream, buffering output using bytestring builders, folds, maps, filters, zips, etc.

  • support for parsing from streams using 'attoparsec'.

  • support for spawning processes and communicating with them using streams.

License: BSD-3-Clause



Package Version Update ID Released Package Hub Version Platforms Subpackages info GA Release 2022-05-09 15 SP4
  • AArch64
  • ppc64le
  • x86-64
  • ghc-io-streams
  • ghc-io-streams-devel info GA Release 2018-08-01 15
  • AArch64
  • ghc-io-streams
  • ghc-io-streams-devel info GA Release 2018-07-31 15
  • ppc64le
  • ghc-io-streams
  • ghc-io-streams-devel info GA Release 2018-07-30 15
  • x86-64
  • ghc-io-streams
  • ghc-io-streams-devel