Lock file

File Format
Name	Lock file
Ontology	Electronic File Formats Temporary files Lock file
Extension(s)	.lck, .lock

Introduction

A lock file is used by an application to indicate there is something going on. For example, to prevent an application to be started twice. Not to be confused with a File lock, although a lock file often has a file lock.

Often a lock file is empty (0 bytes), but it can contain data such as the PID (Process ID).