It's MAX_PATH in Windows (== 260. There's a 32K Unicode-equivalent limit[1]). In Linux it's PATH_MAX, which is (very likely) 4096. That's a bigger number than 260, sure; but it's still a discrete one; instead of, say, ∞.

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[1] 'To specify an extended-length path, use the "\\?\" prefix. For example, "\\?\D:\very long path".' http://msdn.microsoft.com/en-us/library/windows/desktop/aa36...