base-4.14.0.0: Basic libraries
Safe HaskellNone
LanguageHaskell2010

GHC.IO.Handle.Lock

Synopsis

Documentation

data FileLockingNotSupported Source #

Exception thrown by hLock on non-Windows platforms that don't support flock.

Since: base-4.10.0.0

data LockMode Source #

Indicates a mode in which a file should be locked.

Constructors

SharedLock 
ExclusiveLock 

hLock :: Handle -> LockMode -> IO () Source #

If a Handle references a file descriptor, attempt to lock contents of the underlying file in appropriate mode. If the file is already locked in incompatible mode, this function blocks until the lock is established. The lock is automatically released upon closing a Handle.

Things to be aware of:

1) This function may block inside a C call. If it does, in order to be able to interrupt it with asynchronous exceptions and/or for other threads to continue working, you MUST use threaded version of the runtime system.

2) The implementation uses LockFileEx on Windows and flock otherwise, hence all of their caveats also apply here.

3) On non-Windows platforms that don't support flock (e.g. Solaris) this function throws FileLockingNotImplemented. We deliberately choose to not provide fcntl based locking instead because of its broken semantics.

Since: base-4.10.0.0

hTryLock :: Handle -> LockMode -> IO Bool Source #

Non-blocking version of hLock.

Since: base-4.10.0.0

hUnlock :: Handle -> IO () Source #

Release a lock taken with hLock or hTryLock.

Since: base-4.11.0.0