find the root directory of a file in swift

main.swift
func rootDirectory(forFilePath path: String) -> URL? {
    let fileManager = FileManager.default
    
    // Get the URL for the file path
    let fileURL = URL(fileURLWithPath: path)
    
    // Keep moving up the file URL's parent directory until
    // we reach the root directory
    var rootURL: URL? = fileURL
    while let parentURL = rootURL?.deletingLastPathComponent(), parentURL.path != "/" {
        rootURL = parentURL
    }
    
    // Check if the root URL is actually a directory and that it exists
    if let rootURL = rootURL,
       let resourceValues = try? rootURL.resourceValues(forKeys: [.isDirectoryKey]),
       resourceValues.isDirectory ?? false,
       fileManager.fileExists(atPath: rootURL.path) {
        return rootURL
    }
    
    return nil
}
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main.swift
let filePath = "/Users/johndoe/Documents/myfile.txt"
if let rootURL = rootDirectory(forFilePath: filePath) {
    print(rootURL.path) // "/Users"
} else {
    print("Could not find root directory for file path '\(filePath)'")
}
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