Why doesn't ls -U list files in alphabetical order?

drywall_dan

On my Xubuntu install, in some folders, if I list all the files with ls -U , sometimes they are not listed in alphbetical order. For example, once I had it list every single file in alphabetical order except one single file that came before all the others (it started with the letter g and it came before the a 's. All the other g 's were in the place I expected them to be in). How does ls -U decide the order to list files in?

Originally asked by EllipticalInitial on Stack Exchange (superuser) (CC BY-SA 4.0).

uphilltech

Great question — answering as the UphillTech team:

Answers saying -U means "do not sort; list entries in directory order" are right, but the phrase "directory order" or more descriptive "the order in which the files are internally stored" is misleading in some cases. Some filesystems (virtual or FUSE ) do not store anything, they retrieve data on demand. The order you get from ls -U in a filesystem like this may be random(-ish). Imagine a filesystem that aggregates files from several remote servers in one local directory. Let's assume name collisions are not an issue. To list the files as fast as possible the filesystem queries the servers asynchronously, whichever server delivers its listing first will be listed first. Conditions in the...

Full answer by Kamil Maciorowski: https://superuser.stackexchange.com/a/1675754 (CC BY-SA 4.0).

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