The sorting order specified with
--sort only affects the sorting of the files and subdirectories of directories specified on the command line. It does not affect the order in which the paths on the command line are given.
In your case, the command
tar -cf file.tar a b c
b, and then
c last, regardless of the
--sort order specified. If any of these are directories, then using
--sort will affect the order in which the files and subdirectories are added from these directories, but it will not affect the order of
The order in which the operating system returns entries is the same as the one they appear in when using
ls -f. This order is the order in which the directory node stores the entries and may depend on many factors, such as in which order files have been added and deleted (it is dependent on the filesystem implementation).