suplib/src/LockFile.i3


 Copyright 1996-2003 John D. Polstra.
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The LockFile interface allows one to create and remove lock files. It is probably not a good idea to put lock files on NFS-mounted file systems.

INTERFACE LockFile;

IMPORT OSError, Pathname;

TYPE
  T <: ROOT;

PROCEDURE Lock(name: Pathname.T): T
  RAISES {OSError.E};
Creates and locks a file of the given name. Returns NIL if it was already locked. Otherwise, writes the current process-ID into the file, terminated by a newline. Returns a handle that can be used to unlock the file later. The file is automatically unlocked and removed at process termination.

PROCEDURE Unlock(lf: T)
  RAISES {OSError.E};
Unlocks and removes the given lock file.

END LockFile.