import Foundation
let pattern = #"(?s)\h([a-zA-Z0-9]{8})$(?=.*\h\1$)"#
let regex = try! NSRegularExpression(pattern: pattern, options: .anchorsMatchLines)
let testString = #"""
Folder A\Folder C\File three.txt 56efd95f
Folder A\File one.txt b8e1b873
Folder A\Folder B\Folder D\File four.txt 56efd95f
Folder A\Folder B\File two.txt 21e8e9c9
"""#
let stringRange = NSRange(location: 0, length: testString.utf16.count)
let substitutionString = #"$1"#
let result = regex.stringByReplacingMatches(in: testString, range: stringRange, withTemplate: substitutionString)
print(result)
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Swift 5.2, please visit: https://developer.apple.com/documentation/foundation/nsregularexpression