Touched

A Haskell tool for waiting patiently until a file changes, and then doing something.

Install from Hackage with cabal install touched.

System.Touched

System.Touched defines an extremely minimal API: it exports just two types and five functions.

• data Procedure a b

  A type defining a procedure and a handle type. Constructed with either async or cmd by default. Type synonyms:

  • type AsyncCmd = Procedure CreateProcess CmdHandles
  • type AsyncIO = Procedure (IO ()) ThreadId

• onChangeAny :: Bool -> [FilePath] -> Procedure a b -> IO ()

  If any of the files at [FilePath] has changed, the procedure is killed and re-launched. Always launches the procedure the first time, whether a change has happened or not.

  If the first Bool parameter is true, directories are scanned recursively.

• onChangeAll :: Bool -> [FilePath] -> Procedure a b -> IO ()

  Nearly identical to onChangeAny, with the exception that each and every file specified (or all files in a directory, if recursive) must have changed to (re)launch the procedure.

• onChangeFile :: FilePath -> Procedure a b -> IO ()

  Also nearly identical to onChangeAny and onChangeAll but takes a single file or directory and never searches directories recursively.

• async :: IO () -> AsyncIO

  Creates a process out of a Haskell IO thunk.

• cmd :: String -> AsyncCmd

  Creates a process out of a string to be launched in the system shell.

touched-cli

Included with the library is a simple executable for use from a command line. It's pretty easy to use. This is equivalent to the onChangeAny example above:

  touched --call="git commit -am Auto-commit" README.md LICENSE src/System/Touched.md

Known Issues

• When you kill the process you're in, shell processes launched by Touched may continue running. This is on the top of the «to-fix» queue.