Colog.Core.IO

Introduces logging actions working in MonadIO. These actions are very basic and inefficient because they use the String data type. If you don't want to have extra dependencies and performance of logging is not the bottleneck of your application, then these functions should be enough. Otherwise use functions from the Colog.Actions module from the co-log package.

String actions

logStringStdout :: MonadIO m => LogAction m String

Action that prints String to stdout.

>>> logStringStdout <& "foo"
foo

logStringStderr :: MonadIO m => LogAction m String

Action that prints String to stderr.

>>> logStringStderr <& "foo"
foo

logStringHandle :: MonadIO m => Handle -> LogAction m String

Action that prints String to Handle.

>>> logStringHandle stderr <& "foo"
foo

withLogStringFile :: MonadIO m => FilePath -> (LogAction m String -> IO r) -> IO r

Action that prints String to file. Instead of returning LogAction it's implemented in continuation-passing style because it's more efficient to open file only once at the start of the application and write to Handle instead of opening file each time we need to write to it.

Opens file in AppendMode.

>>> logger action = action <& "foo"
>>> withLogStringFile "/dev/stdout" logger
foo

Show actions

logPrint :: forall a m. (Show a, MonadIO m) => LogAction m a

Action that prints to stdout using Show.

>>> logPrint <& 5
5

logPrintStderr :: forall a m. (Show a, MonadIO m) => LogAction m a

Action that prints to stderr using Show.

>>> logPrintStderr <& 5
5

logPrintHandle :: forall a m. (Show a, MonadIO m) => Handle -> LogAction m a

Action that prints to a Handle using Show.

>>> logPrintHandle stderr <& 5
5

withLogPrintFile :: forall a m r. (Show a, MonadIO m) => FilePath -> (LogAction m a -> IO r) -> IO r

Action that prints to a file using Show. See withLogStringFile for details.

Various combinators

liftLogIO :: MonadIO m => LogAction IO msg -> LogAction m msg

Lifts a LogAction over IO into a more general Monad.

>>> logToStdout = LogAction putStrLn
>>> liftLogIO logToStdout <& "foo"
foo