-- Hoogle documentation, generated by Haddock
-- See Hoogle, http://www.haskell.org/hoogle/


-- | Run an IO action protected by a pidfile
--   
--   Run an IO action protected by a pidfile. This will prevent more than
--   one instance of your program to run at a time.
@package pidfile
@version 0.1.0.4


-- | Run an IO action protected by a pidfile. This will prevent more than
--   one instance of your program to run at a time.
module System.PidFile

-- | <tt><a>withPidFile</a> path act</tt> creates a pidfile at the
--   specified <tt>path</tt> containing the Process ID of the current
--   process. Then <tt>act</tt> is run, the pidfile is removed and the
--   result of <tt>act</tt> returned wrapped in a <a>Just</a>.
--   
--   If the pidfile already exists, <tt>act</tt> is not run, and
--   <a>Nothing</a> is returned. Any other error while creating the pidfile
--   results in an error.
--   
--   If an exception is raised in <tt>act</tt>, the pidfile is removed
--   before the exception is propagated.
--   
--   The pidfile is created with <tt>O_CREAT</tt> and <tt>O_EXCL</tt> flags
--   to ensure that an already existing pidfile is never accidentally
--   overwitten.
withPidFile :: FilePath -> IO a -> IO (Maybe a)