Copyright | 2015 Joey Hess <id@joeyh.name> |
---|---|
License | BSD-2-clause |
Safe Haskell | None |
Language | Haskell98 |
Concurrent output handling.
import Control.Concurrent.Async import System.Console.Concurrent main = withConcurrentOutput $ do outputConcurrent "washed the car\n" `concurrently` outputConcurrent "walked the dog\n" `concurrently` createProcessConcurrent (proc "ls" [])
Synopsis
- withConcurrentOutput :: (MonadIO m, MonadMask m) => m a -> m a
- class Outputable v where
- outputConcurrent :: Outputable v => v -> IO ()
- errorConcurrent :: Outputable v => v -> IO ()
- createProcessConcurrent :: CreateProcess -> IO (Maybe Handle, Maybe Handle, Maybe Handle, ProcessHandle)
- createProcessForeground :: CreateProcess -> IO (Maybe Handle, Maybe Handle, Maybe Handle, ProcessHandle)
- flushConcurrentOutput :: IO ()
- lockOutput :: (MonadIO m, MonadMask m) => m a -> m a
- type ConcurrentProcessHandle = ProcessHandle
- waitForProcessConcurrent :: ConcurrentProcessHandle -> IO ExitCode
- data OutputBuffer
- data StdHandle
- bufferOutputSTM :: Outputable v => StdHandle -> v -> STM ()
- outputBufferWaiterSTM :: (OutputBuffer -> (OutputBuffer, OutputBuffer)) -> STM (StdHandle, OutputBuffer)
- waitAnyBuffer :: OutputBuffer -> (OutputBuffer, OutputBuffer)
- waitCompleteLines :: OutputBuffer -> (OutputBuffer, OutputBuffer)
- emitOutputBuffer :: StdHandle -> OutputBuffer -> IO ()
Concurrent output
withConcurrentOutput :: (MonadIO m, MonadMask m) => m a -> m a Source #
Use this around any actions that use outputConcurrent
or createProcessConcurrent
, unless
displayConsoleRegions
is being used.
This is necessary to ensure that buffered concurrent output actually gets displayed before the program exits.
class Outputable v where Source #
Values that can be output.
Instances
Outputable String Source # | |
Outputable Text Source # | Note that using a lazy Text as an Outputable value will buffer it all in memory. |
Outputable Text Source # | |
outputConcurrent :: Outputable v => v -> IO () Source #
Displays a value to stdout.
Uses locking to ensure that the whole output occurs atomically even when other threads are concurrently generating output.
No newline is appended to the value, so if you want a newline, be sure to include it yourself.
When something else is writing to the console at the same time, this does not block. It buffers the value, so it will be displayed once the other writer is done.
When outputConcurrent is used within a call to
displayConsoleRegions
, the output is displayed
above the currently open console regions. Only lines ending in a newline
are displayed in this case (it uses waitCompleteLines
).
errorConcurrent :: Outputable v => v -> IO () Source #
Like outputConcurrent
, but displays to stderr.
(Does not throw an exception.)
createProcessConcurrent :: CreateProcess -> IO (Maybe Handle, Maybe Handle, Maybe Handle, ProcessHandle) Source #
Wrapper around createProcess
that prevents
multiple processes that are running concurrently from writing
to stdout/stderr at the same time.
If the process does not output to stdout or stderr, it's run by createProcess entirely as usual. Only processes that can generate output are handled specially:
A process is allowed to write to stdout and stderr in the usual way, assuming it can successfully take the output lock.
When the output lock is held (ie, by another concurrent process,
or because outputConcurrent
is being called at the same time),
the process is instead run with its stdout and stderr
redirected to a buffer. The buffered output will be displayed as soon
as the output lock becomes free.
Note that the the process is waited for by a background thread, so unlike createProcess, neglecting to call waitForProcess will not result in zombie processess.
createProcessForeground :: CreateProcess -> IO (Maybe Handle, Maybe Handle, Maybe Handle, ProcessHandle) Source #
Wrapper around createProcess
that makes sure a process
is run in the foreground, with direct access to stdout and stderr.
Useful when eg, running an interactive process.
Note that the the process is waited for by a background thread, so unlike createProcess, neglecting to call waitForProcess will not result in zombie processess.
flushConcurrentOutput :: IO () Source #
Blocks until any processes started by createProcessConcurrent
have
finished, and any buffered output is displayed. Also blocks while
lockOutput
is is use.
withConcurrentOutput
calls this at the end, so you do not normally
need to use this.
lockOutput :: (MonadIO m, MonadMask m) => m a -> m a Source #
Holds a lock while performing an action. This allows the action to perform its own output to the console, without using functions from this module.
While this is running, other threads that try to lockOutput will block.
Any calls to outputConcurrent
and createProcessConcurrent
will not
block, but the output will be buffered and displayed only once the
action is done.
type ConcurrentProcessHandle = ProcessHandle Source #
This alias is provided to avoid breaking backwards compatibility.
waitForProcessConcurrent :: ConcurrentProcessHandle -> IO ExitCode Source #
Same as waitForProcess
; provided to avoid breaking backwards
compatibility.
Low level access to the output buffer
data OutputBuffer Source #
Buffered output.
Instances
Eq OutputBuffer Source # | |
Defined in System.Console.Concurrent.Internal (==) :: OutputBuffer -> OutputBuffer -> Bool # (/=) :: OutputBuffer -> OutputBuffer -> Bool # |
bufferOutputSTM :: Outputable v => StdHandle -> v -> STM () Source #
Adds a value to the output buffer for later display.
Note that buffering large quantities of data this way will keep it
resident in memory until it can be displayed. While outputConcurrent
uses temp files if the buffer gets too big, this STM function cannot do
so.
outputBufferWaiterSTM :: (OutputBuffer -> (OutputBuffer, OutputBuffer)) -> STM (StdHandle, OutputBuffer) Source #
A STM action that waits for some buffered output to become available, and returns it.
The function can select a subset of output when only some is desired; the fst part is returned and the snd is left in the buffer.
This will prevent it from being displayed in the usual way, so you'll
need to use emitOutputBuffer
to display it yourself.
waitAnyBuffer :: OutputBuffer -> (OutputBuffer, OutputBuffer) Source #
waitCompleteLines :: OutputBuffer -> (OutputBuffer, OutputBuffer) Source #
Use with outputBufferWaiterSTM
to make it only return buffered
output that ends with a newline. Anything buffered without a newline
is left in the buffer.
emitOutputBuffer :: StdHandle -> OutputBuffer -> IO () Source #
Emits the content of the OutputBuffer to the Handle
If you use this, you should use lockOutput
to ensure you're the only
thread writing to the console.