Issue #18947 has been updated by matz (Yukihiro Matsumoto). Please go ahead with this approach. Relying on an undocumented bit is not ideal, but the failure mode decides it for me: if the bit ever stops working, we are back to today's 260 character limit, not broken. That is a cheap downside for fixing a four year old problem that the `\\?\` alternative cannot fully fix anyway. I leave the embedder question to you. Whichever way you go, please document the limitations you found in [#note-9](https://bugs.ruby-lang.org/issues/18947#note-9): the 255 character limit per path component, and that spawning a child process from a working directory longer than 260 characters still fails. Matz. ---------------------------------------- Bug #18947: Unexpected Errno::ENAMETOOLONG on Windows https://bugs.ruby-lang.org/issues/18947#change-118414 * Author: inversion (Yura Babak) * Status: Open * Assignee: windows * ruby -v: ruby 3.1.2p20 (2022-04-12 revision 4491bb740a) [x64-mingw-ucrt] * Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN ---------------------------------------- On Windows 10, I am working on a script to copy a complex folder structure. Pathname and FileUtils work fine for me until there is a folder with a **very long path** (>260 chars). Normally you cannot access such a folder with Ruby. The next operations will raise `Errno::ENOENT` ``` ruby Pathname.new(300_chars_path).children FileUtils.mkpath(300_chars_path) ``` But there is a way in Windows to remove the MAX_PATH limitation. You can find a small .reg file in this article: https://docs.microsoft.com/en-us/windows/win32/fileio/maximum-file-path-limi... After changing this system option, things start to work strangely in Ruby. This will now raise `Errno::ENAMETOOLONG`: ``` ruby Pathname.new(300_chars_path).children ``` But at the same time, you can create a folder with such a long path and write-read a file in it ``` ruby FileUtils.mkpath(300_chars_path) file = Pathname.new(300_chars_path+'/file.txt') file.write 'oooooooooo' puts Pathname.new(300_chars_path+'/file.txt').read ``` So you can work with individual items but attempts to list such folders' content fail (`.children`, `.glob`, `.copy`, etc). In my case, deep `.glob` is broken for all the parent folders of that deep long-path folder (( The only way I found for listing is ``` ruby require 'win32ole' fso = WIN32OLE.new 'Scripting.FileSystemObject' for file in fso.GetFolder(300_chars_path).files file.name file.path.length end ``` But using this workaround breaks all my code workflow built on top of Pathname and FileUtils ((. So for me, it looks like some operations with long-path folders are not working just because in Ruby there is a check for the path length and not a real operation problem. And in some places (see .mkpath) there is no such check and all works fine. Also notice that other applications on Windows have no problems with long-path folders (like Total Commander). Please consider reviewing if we really need to raise `Errno::ENAMETOOLONG` if the `LongPathsEnabled` option is enabled in the Windows registry. -- https://bugs.ruby-lang.org/