> It would be quite helpful for me if if I could use join with
numerically sorted key fields, without having to alpha sort the
files on the key fields, perform join, then numerically resort the
files on the key fields
Yes, that would be a nice feature to add. Perhaps you could write
the code and documentation? The behavior should be consistent
with that of sort -n and/or sort -g, and should use similarly-named
options.
Of course join can't sort numerically by default, because that would
break existing scripts and POSIX doesn't allow it. See
<http://www.opengroup.org/onlinepubs/009695399/utilities/join.html>.
But it sort numerically if you pass it an option.