ceph-csi/vendor/github.com/fsnotify/fsnotify/README.md
Madhu Rajanna 9c8de9471e rebase: update kubernetes to 1.26.1
update kubernetes and its dependencies
to v1.26.1

Signed-off-by: Madhu Rajanna <madhupr007@gmail.com>
2023-02-03 08:55:43 +00:00

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Markdown

fsnotify is a Go library to provide cross-platform filesystem notifications on
Windows, Linux, macOS, and BSD systems.
Go 1.16 or newer is required; the full documentation is at
https://pkg.go.dev/github.com/fsnotify/fsnotify
**It's best to read the documentation at pkg.go.dev, as it's pinned to the last
released version, whereas this README is for the last development version which
may include additions/changes.**
---
Platform support:
| Adapter | OS | Status |
| --------------------- | ---------------| -------------------------------------------------------------|
| inotify | Linux 2.6.32+ | Supported |
| kqueue | BSD, macOS | Supported |
| ReadDirectoryChangesW | Windows | Supported |
| FSEvents | macOS | [Planned](https://github.com/fsnotify/fsnotify/issues/11) |
| FEN | Solaris 11 | [In Progress](https://github.com/fsnotify/fsnotify/pull/371) |
| fanotify | Linux 5.9+ | [Maybe](https://github.com/fsnotify/fsnotify/issues/114) |
| USN Journals | Windows | [Maybe](https://github.com/fsnotify/fsnotify/issues/53) |
| Polling | *All* | [Maybe](https://github.com/fsnotify/fsnotify/issues/9) |
Linux and macOS should include Android and iOS, but these are currently untested.
Usage
-----
A basic example:
```go
package main
import (
"log"
"github.com/fsnotify/fsnotify"
)
func main() {
// Create new watcher.
watcher, err := fsnotify.NewWatcher()
if err != nil {
log.Fatal(err)
}
defer watcher.Close()
// Start listening for events.
go func() {
for {
select {
case event, ok := <-watcher.Events:
if !ok {
return
}
log.Println("event:", event)
if event.Has(fsnotify.Write) {
log.Println("modified file:", event.Name)
}
case err, ok := <-watcher.Errors:
if !ok {
return
}
log.Println("error:", err)
}
}
}()
// Add a path.
err = watcher.Add("/tmp")
if err != nil {
log.Fatal(err)
}
// Block main goroutine forever.
<-make(chan struct{})
}
```
Some more examples can be found in [cmd/fsnotify](cmd/fsnotify), which can be
run with:
% go run ./cmd/fsnotify
FAQ
---
### Will a file still be watched when it's moved to another directory?
No, not unless you are watching the location it was moved to.
### Are subdirectories watched too?
No, you must add watches for any directory you want to watch (a recursive
watcher is on the roadmap: [#18]).
[#18]: https://github.com/fsnotify/fsnotify/issues/18
### Do I have to watch the Error and Event channels in a goroutine?
As of now, yes (you can read both channels in the same goroutine using `select`,
you don't need a separate goroutine for both channels; see the example).
### Why don't notifications work with NFS, SMB, FUSE, /proc, or /sys?
fsnotify requires support from underlying OS to work. The current NFS and SMB
protocols does not provide network level support for file notifications, and
neither do the /proc and /sys virtual filesystems.
This could be fixed with a polling watcher ([#9]), but it's not yet implemented.
[#9]: https://github.com/fsnotify/fsnotify/issues/9
Platform-specific notes
-----------------------
### Linux
When a file is removed a REMOVE event won't be emitted until all file
descriptors are closed; it will emit a CHMOD instead:
fp := os.Open("file")
os.Remove("file") // CHMOD
fp.Close() // REMOVE
This is the event that inotify sends, so not much can be changed about this.
The `fs.inotify.max_user_watches` sysctl variable specifies the upper limit for
the number of watches per user, and `fs.inotify.max_user_instances` specifies
the maximum number of inotify instances per user. Every Watcher you create is an
"instance", and every path you add is a "watch".
These are also exposed in `/proc` as `/proc/sys/fs/inotify/max_user_watches` and
`/proc/sys/fs/inotify/max_user_instances`
To increase them you can use `sysctl` or write the value to proc file:
# The default values on Linux 5.18
sysctl fs.inotify.max_user_watches=124983
sysctl fs.inotify.max_user_instances=128
To make the changes persist on reboot edit `/etc/sysctl.conf` or
`/usr/lib/sysctl.d/50-default.conf` (details differ per Linux distro; check your
distro's documentation):
fs.inotify.max_user_watches=124983
fs.inotify.max_user_instances=128
Reaching the limit will result in a "no space left on device" or "too many open
files" error.
### kqueue (macOS, all BSD systems)
kqueue requires opening a file descriptor for every file that's being watched;
so if you're watching a directory with five files then that's six file
descriptors. You will run in to your system's "max open files" limit faster on
these platforms.
The sysctl variables `kern.maxfiles` and `kern.maxfilesperproc` can be used to
control the maximum number of open files.
### macOS
Spotlight indexing on macOS can result in multiple events (see [#15]). A temporary
workaround is to add your folder(s) to the *Spotlight Privacy settings* until we
have a native FSEvents implementation (see [#11]).
[#11]: https://github.com/fsnotify/fsnotify/issues/11
[#15]: https://github.com/fsnotify/fsnotify/issues/15