You might want to take a look at .canonicalPathKey (NSURLCanonicalPathKey). On Apple platforms a lot of the standard UNIXy paths exist within /private/, with corresponding symlinks from the root. So /etc/ is actually /private/etc/.
$ ls -ld /etc
lrwxr-xr-x@ 1 root wheel 11 10 Dec 2016 /etc -> private/etc
$ ls -ld /private/etc
drwxr-xr-x 131 root wheel 4454 16 Jan 08:33 /private/etc
If you don’t canonicalise the paths you can get tripped up by this.
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Apple Developer Relations, Developer Technical Support, Core OS/Hardware
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