T. R. Bernstein
8af25be549
Patterns such as `.*` or `@*` are matched against an item's own name with `fnmatch`, in the same places as excluded names: resolving a tree, extending a watch to a directory that appears later, and delivering events. Dependents that prune large trees can now skip whole families of directories without listing each name.
3.1 KiB
Watching Directory Trees
Monitor an entire directory hierarchy for filesystem events.
Overview
The Linux inotify API watches individual directories — it does not descend into subdirectories automatically. The Inotify/Inotify actor offers two convenience methods that handle the recursion for you.
Recursive Watch
Call Inotify/Inotify/addRecursiveWatch(forDirectory:mask:) to walk the directory tree once and install a watch on every subdirectory that exists at the time of the call:
let inotify = try Inotify()
let descriptors = try await inotify.addRecursiveWatch(
forDirectory: "/home/user/project",
mask: [.create, .modify, .delete]
)
The returned array contains one watch descriptor per directory. Subdirectories created after this call are not covered.
Automatic Subtree Watching
When you also want future subdirectories to be picked up, use Inotify/Inotify/addWatchWithAutomaticSubtreeWatching(forDirectory:mask:) instead:
let descriptors = try await inotify.addWatchWithAutomaticSubtreeWatching(
forDirectory: "/home/user/project",
mask: [.create, .modify, .delete]
)
Internally this listens for CREATE and MOVED_TO events carrying the InotifyEventMask/isDir flag and installs new watches with the same mask on the subdirectory and its subtree whenever one appears. Items that already exist inside such a subdirectory are reported with InotifyEvent/synthesized set to true, since the kernel never produces events for them; a synthesized event may duplicate a kernel event for the same item.
When a directory is moved out of the watched tree, the watches on it and on its subdirectories are removed, so no events are reported under the stale path.
Excluding Directories
When watching large trees you often want to skip certain subdirectories entirely — version-control metadata, build artefacts, dependency caches, and so on. Call Inotify/Inotify/exclude(names:) or Inotify/Inotify/exclude(patterns:) before adding a recursive or automatic-subtree watch:
let inotify = try Inotify()
await inotify.exclude(names: ".git", "node_modules", ".build")
await inotify.exclude(patterns: ".*", "*.tmp")
try await inotify.addWatchWithAutomaticSubtreeWatching(
forDirectory: "/home/user/project",
mask: .allEvents
)
Excluded names and patterns are matched against the last path component of each directory during resolution, against a directory that appears later before a watch is extended to it, and against every event, so you never receive events for excluded items. A pattern is matched the way the shell matches file names: * and ? stand for any characters and […] for a set of characters; a leading dot needs no special treatment.
Choosing the Right Method
| Method | Covers existing subdirectories | Covers new subdirectories |
|---|---|---|
Inotify/Inotify/addWatch(path:mask:) |
No | No |
Inotify/Inotify/addRecursiveWatch(forDirectory:mask:) |
Yes | No |
Inotify/Inotify/addWatchWithAutomaticSubtreeWatching(forDirectory:mask:) |
Yes | Yes |