(info "(coreutils) Sorting files for join") needs to talk about numeric order.
$ seq 111|join --check-order - /dev/null join: -:10: is not sorted: 10 So the info manual needs to mention 'Even though your files might be in perfect "sort --numeric-sort" order, you need to make them into plain "sort" order first. Sorry. At least you'll get the same number of joins.' Or, add a new join -n option. The join man page could now say: '-n: use numeric comparisons. Note sort order also needs to be "sort -n" order.' And / or mention how the user might tinker with LC_NUMERIC and / or LC_COLLATE to somehow achieve numeric sorting...
