HORIZON HASKELLDocslts/ghc-9.10.x248f8f02026-10-05Search names, modules, packages, or :: a typeCtrl K

GHC 9.10.3 · lts/ghc-9.10.x · 248f8f0 · 2026-10-05

Modulestreamly-core-0.2.2Haskell2010

Streamly.FileSystem.File

Warning: The API of this module is subject to change in future releases. Especially the type for representing paths may change from FilePath to something else.

Read and write streams and arrays to and from files specified by their paths in the file system. Unlike the handle based APIs which can have a read/write session consisting of multiple reads and writes to the handle, these APIs are one shot read or write APIs. These APIs open the file handle, perform the requested operation and close the handle. These are safer compared to the handle based APIs as there is no possibility of a file descriptor leakage.

Example1 expression
import qualified Streamly.FileSystem.File as File
  • 7 values

Streaming IO

0 declarations

Stream data to or from a file or device sequentially. When reading, the stream is lazy and generated on-demand as the consumer consumes it. Read IO requests to the IO device are performed in chunks limited to a maximum size of 32KiB, this is referred to as defaultChunkSize in the documentation. One IO request may or may not read the full chunk. If the whole stream is not consumed, it is possible that we may read slightly more from the IO device than what the consumer needed. Unless specified otherwise in the API, writes are collected into chunks of defaultChunkSize before they are written to the IO device.

File IO Using Handle

valuewithFile
  1. :: (MonadIO m, MonadCatch m)
  2. => FilePath
  3. -> IOMode
  4. -> Handle -> Stream m a
  5. -> Stream m a
#

withFile name mode act opens a file using openFile and passes the resulting handle to the computation act. The handle will be closed on exit from withFile, whether by normal termination or by raising an exception. If closing the handle raises an exception, then this exception will be raised by withFile rather than any exception raised by act.

Pre-release

Streams

valueread :: (MonadIO m, MonadCatch m) => FilePath -> Stream m Word8
#

Generate a stream of bytes from a file specified by path. The stream ends when EOF is encountered. File is locked using multiple reader and single writer locking mode.

Pre-release

valuereadChunks
  1. :: (MonadIO m, MonadCatch m)
  2. => FilePath
  3. -> Stream m (Array Word8)
#

readChunks file reads a stream of arrays from file file. The maximum size of a single array is limited to defaultChunkSize. The actual size read may be less than defaultChunkSize.

readChunks = readChunksWith defaultChunkSize

Pre-release

Folds

valuewrite :: (MonadIO m, MonadCatch m) => FilePath -> Fold m Word8 ()
#

Write a byte stream to a file. Accumulates the input in chunks of up to Streamly.Internal.Data.Array.Type.defaultChunkSize before writing to the IO device.

Pre-release

valuewriteWith :: (MonadIO m, MonadCatch m) => Int -> FilePath -> Fold m Word8 ()
#

writeWith chunkSize handle writes the input stream to handle. Bytes in the input stream are collected into a buffer until we have a chunk of size chunkSize and then written to the IO device.

Pre-release