A file used to ensure that only one process at a time can access data in a particular file.

a file placed in the /etc/locks directory when a program uses a communications device or contacts a remote system

a small file, usually of zero length (empty) that is used to indicate a running process or ownership of a directory

In PowerAda, a file used to implement an advisory read-lock or write-lock on a sublibrary. This file is in the sublibrary directory and is called adalockfile. Deleting this file defeats locking on that sublibrary.

In multiprocess applications, a system file on disk that the sharing processes use to control their access to shared data or devices.