https://blog.krzyzanowskim.com/2019/12/05/url-bookmark-yes-and-no/

urlbookmark.swift

// Marcin Krzyzanowski
// blog.krzyzanowskim.com

import Foundation

extension URLResourceKey {
  static let bookmarkAllPropertiesKey = URLResourceKey("NSURLBookmarkAllPropertiesKey")
  static let fileIDKey = URLResourceKey("_NSURLFileIDKey")
  static let inode = URLResourceKey.fileIDKey
}

private func getInode(for fileURL: URL) throws -> Int {
  // ls -i /tmp/file.txt
  var tmp = fileURL
  tmp.removeCachedResourceValue(forKey: .inode)
  return try fileURL.resourceValues(forKeys: [.inode]).allValues[.inode] as! Int
}

private func checkAtomicWrite(for fileURL: URL) throws -> (Int, Int) {
  let inodeBefore = try getInode(for: fileURL)
  try "foobar".write(to: fileURL, atomically: true, encoding: .utf8)
  let inodeAfter = try getInode(for: fileURL)
  return (inodeBefore, inodeAfter)
}

private func checkNonAtomicWrite(for fileURL: URL) throws -> (Int, Int) {
  let inodeBefore = try getInode(for: fileURL)
  try "foobar".write(to: fileURL, atomically: false, encoding: .utf8)
  let inodeAfter = try getInode(for: fileURL)
  return (inodeBefore, inodeAfter)
}

// Check inode values

let fileURL = URL(fileURLWithPath: "/tmp/file.txt")

// Create empty file
if FileManager.default.fileExists(atPath: fileURL.path) {
  FileManager.default.removeItem(at: fileURL)
}
FileManager.default.createFile(atPath: fileURL.path, contents: nil, attributes: nil)

// Test inode changes

let (inodeBeforeAtomic, inodeAfterAtomic) = try checkAtomicWrite(for: fileURL)
if (inodeBeforeAtomic != inodeAfterAtomic) {
  print("[Atomic] inode value changed: \(inodeBeforeAtomic) -> \(inodeAfterAtomic)")
}

let (inodeBeforeNonAtomic, inodeAfterNonAtomic) = try checkNonAtomicWrite(for: fileURL)
if (inodeBeforeNonAtomic != inodeAfterNonAtomic) {
  print("[Non atomic] inode value changed: \(inodeBeforeNonAtomic) -> \(inodeAfterNonAtomic)")
}

// Check bookmarks

do {
  // Create bookmark
  let bookmark = try fileURL.bookmarkData()

  // Modify file
  try "foobar".write(to: fileURL, atomically: true, encoding: .utf8)

  // Move file to /tmp/file.txt.bak
   try FileManager.default.moveItem(at: fileURL, to: fileURL.appendingPathExtension("bak"))

  // Try to use bookmark 💥 Error: The file doesn’t exist.
  var bookmarkIsStale = false
  try URL(resolvingBookmarkData: bookmark, bookmarkDataIsStale: &bookmarkIsStale)
} catch {
  print(error)
}

// Cleanup
FileManager.default.removeItem(at: fileURL.appendingPathExtension("bak"))