A file change log tracks changes to the namespace (files and directories) of a file system

File system

A file system is a means to organize data expected to be retained after a program terminates by providing procedures to store, retrieve and update data, as well as manage the available space on the device which contain it. A file system organizes data in an efficient manner and is tuned to the...

. Depending on the implementation, a file change log will record changes such as creates, links, unlinks (deletions), renamed files, data changes, and metadata changes (for example, ACLs

Access control list

An access control list , with respect to a computer file system, is a list of permissions attached to an object. An ACL specifies which users or system processes are granted access to objects, as well as what operations are allowed on given objects. Each entry in a typical ACL specifies a subject...

 and permissions). A file change log can be accessed as a file in the file system, or hidden and accessed only programmatically.

A file change log differs from a file system's journal

Journaling file system

A journaling file system is a file system that keeps track of the changes that will be made in a journal before committing them to the main file system...

.

Such a log can serve at least two purposes.

First, some applications must scan an entire file system to discover changes since their last scan. By reading a file change log, they can avoid this scan. Scanning applications include backup utilities

Backup software

Backup software are computer programs used to perform backup; they create supplementary exact copies of files, databases or entire computers. These programs may later use the supplementary copies to restore the original contents in the event of data loss....

, web crawler

Web crawler

A Web crawler is a computer program that browses the World Wide Web in a methodical, automated manner or in an orderly fashion. Other terms for Web crawlers are ants, automatic indexers, bots, Web spiders, Web robots, or—especially in the FOAF community—Web scutters.This process is called Web...

, search engine

Search engine

A search engine is an information retrieval system designed to help find information stored on a computer system. The search results are usually presented in a list and are commonly called hits. Search engines help to minimize the time required to find information and the amount of information...

s, and replication programs.

Second, the log can serve as an audit record for activity in a file system.