| Safe Haskell | Safe |
|---|---|
| Language | Haskell2010 |
System.FileLock
Description
This module provides a portable interface to file locks as a mechanism for inter-process synchronization.
Each file lock is associated with a file. When taking a lock, the assiciated
file is created if it's not present, then the file is locked in an
OS-dependent way. While the lock is being held, no other process or
thread can take it, unless the specified SharedExclusive values
allow it.
All locks held by a process are released when the process exits. They can
also be explicitly released using unlockFile.
It is not recommended to open or otherwise use lock files for other
purposes, because it tends to expose differences between operating systems.
For example, on Windows openFile for a lock file will fail when
the lock is held, but on Unix it won't.
Note on the implementation: currently the module uses flock(2) on non-Windows platforms, and LockFileEx on Windows.
- data FileLock
- data SharedExclusive
- lockFile :: FilePath -> SharedExclusive -> IO FileLock
- tryLockFile :: FilePath -> SharedExclusive -> IO (Maybe FileLock)
- unlockFile :: FileLock -> IO ()
- withFileLock :: FilePath -> SharedExclusive -> (FileLock -> IO a) -> IO a
- withTryFileLock :: FilePath -> SharedExclusive -> (FileLock -> IO a) -> IO (Maybe a)
Documentation
data SharedExclusive Source #
A type of lock to be taken.
Constructors
| Shared | Other process can hold a shared lock at the same time. |
| Exclusive | No other process can hold a lock, shared or exclusive. |
lockFile :: FilePath -> SharedExclusive -> IO FileLock Source #
Take a lock. This function blocks until the lock is available.
tryLockFile :: FilePath -> SharedExclusive -> IO (Maybe FileLock) Source #
Try to take a lock. This function does not block. If the lock is not immediately available, it returns Nothing.
unlockFile :: FileLock -> IO () Source #
Release the lock.
withFileLock :: FilePath -> SharedExclusive -> (FileLock -> IO a) -> IO a Source #
Perform some action with a lock held. Blocks until the lock is available.
withTryFileLock :: FilePath -> SharedExclusive -> (FileLock -> IO a) -> IO (Maybe a) Source #
Perform sme action with a lock held. Non-blocking.