Finding unescaped spaces in path strings via Regular Expression negative look-behind

regex_neg_lookbehind.swift

//: Playground - noun: a place where people can play

import Foundation

var path = "/abc/def ghi/jkg\\ lmn/opq"

let reEscapedSpaces = "^.*\\\\ .*$"  // simple
let reUnescapedSpaces = "^.*(?<!\\\\) .*$". // negative look-behind

if path.range(of: reUnescapedSpaces, options: .regularExpression) != nil {
    print("YES match")
} else {
    print("NO match")
}