Re: Inconsistent list output

[Paul Eggert]

On 9/8/22 14:23, Andreas Dilger wrote:
> GNU "ls" has this unfortunate misfeature of reading the whole directory to 
> read+stat every entry in a directory to determine field width before displaying anything 
> (even if unsorted), and this is a real problem for large directories on a network 
> filesystem. Please do not inflict this on tar.

Yes. In ls's defense, ls output is normally sorted, and the 'ls -U' use 
case is so rare that I expect we haven't bothered to optimize it. Tar is 
different, though, since it never sorts its output.

The algorithm Tar uses is: output "user/group size" in a field of width 
19. If that's too narrow, widen the field width to the minimum 
necessary. This may yield stairstepping, but if we increased 19 to a 
larger value we'd be more likley to waste valuable screen real estate. 
See Tar's simple_print_header function for details.

For what it's worth, people who want reproducible builds should be 
running tar with options like "--owner=0 --group=0 --numeric-owner" 
anyway, and tarballs created that way avoid the stairstepping problem.