---
title: File System Events
framework: Core Services
role: collectionGroup
role_heading: API Collection
path: coreservices/file_system_events
---

# File System Events

Get notifications when the contents of a directory hierarchy change.

## Overview

Overview The file system events API provides a way for your application to ask for notification when the contents of a directory hierarchy are modified. For example, your application can use this to quickly detect when the user modifies a file within a project bundle using another application. It also provides a lightweight way to determine whether the contents of a directory hierarchy have changed since your application last examined them. For example, a backup application can use this to determine what files have changed since a given time stamp or a given event ID.

## Topics

### Functions

- [FSEventStreamCopyDescription(_:)](coreservices/1442676-fseventstreamcopydescription.md)
- [FSEventStreamCopyPathsBeingWatched(_:)](coreservices/1447917-fseventstreamcopypathsbeingwatch.md)
- [FSEventStreamCreate(_:_:_:_:_:_:_:)](coreservices/1443980-fseventstreamcreate.md)
- [FSEventStreamCreateRelativeToDevice(_:_:_:_:_:_:_:_:)](coreservices/1447341-fseventstreamcreaterelativetodev.md)
- [FSEventStreamFlushAsync(_:)](coreservices/1441727-fseventstreamflushasync.md)
- [FSEventStreamFlushSync(_:)](coreservices/1445629-fseventstreamflushsync.md)
- [FSEventStreamGetDeviceBeingWatched(_:)](coreservices/1449675-fseventstreamgetdevicebeingwatch.md)
- [FSEventStreamGetLatestEventId(_:)](coreservices/1446030-fseventstreamgetlatesteventid.md)
- [FSEventStreamInvalidate(_:)](coreservices/1446990-fseventstreaminvalidate.md)
- [FSEventStreamRelease(_:)](coreservices/1445989-fseventstreamrelease.md)
- [FSEventStreamRetain(_:)](coreservices/1444986-fseventstreamretain.md)
- [FSEventStreamScheduleWithRunLoop(_:_:_:)](coreservices/1447824-fseventstreamschedulewithrunloop.md)
- [FSEventStreamSetDispatchQueue(_:_:)](coreservices/1444164-fseventstreamsetdispatchqueue.md)
- [FSEventStreamSetExclusionPaths(_:_:)](coreservices/1444666-fseventstreamsetexclusionpaths.md)
- [FSEventStreamShow(_:)](coreservices/1444302-fseventstreamshow.md)
- [FSEventStreamStart(_:)](coreservices/1448000-fseventstreamstart.md)
- [FSEventStreamStop(_:)](coreservices/1447673-fseventstreamstop.md)
- [FSEventStreamUnscheduleFromRunLoop(_:_:_:)](coreservices/1441982-fseventstreamunschedulefromrunlo.md)
- [FSEventsCopyUUIDForDevice(_:)](coreservices/1444453-fseventscopyuuidfordevice.md)
- [FSEventsGetCurrentEventId()](coreservices/1442917-fseventsgetcurrenteventid.md)
- [FSEventsGetLastEventIdForDeviceBeforeTime(_:_:)](coreservices/1449772-fseventsgetlasteventidfordeviceb.md)
- [FSEventsPurgeEventsForDeviceUpToEventId(_:_:)](coreservices/1447985-fseventspurgeeventsfordeviceupto.md)

### Enumerations

- [FSEventStreamCreateFlags](coreservices/file_system_events/1455376-fseventstreamcreateflags.md)
- [FSEventStreamEventFlags](coreservices/file_system_events/1455361-fseventstreameventflags.md)

### Data Types

- [FSEventStreamCallback](coreservices/fseventstreamcallback.md)
- [FSEventStreamCreateFlags](coreservices/fseventstreamcreateflags.md)
- [FSEventStreamEventFlags](coreservices/fseventstreameventflags.md)
- [FSEventStreamEventId](coreservices/fseventstreameventid.md)
- [FSEventStreamRef](coreservices/fseventstreamref.md)

### Constants

- [kFSEventStreamEventExtendedDataPathKey](coreservices/kfseventstreameventextendeddatapathkey.md)
- [kFSEventStreamEventExtendedFileIDKey](coreservices/kfseventstreameventextendedfileidkey.md)

## See Also

### Related Documentation

- [File System Events Programming Guide](apple-archive/documentation/Darwin/Conceptual/FSEvents_ProgGuide/Introduction.md)