[coreutils] [PATCH] don't warn about disorder against empty input

[Pádraig Brady]

I notice that join doesn't warn about disorder
when there are no mismatches between the two files,
which is a good thing.

$ join -a1 <(printf '1\n0\n') <(printf '1\n0\n')
1
0

However it does warn if there is no input
in one of the files. I'm inclined to think that
the following should be treated as above?

$ join -a1 <(printf '1\n0\n') /dev/null
1
join: file 1 is not in sorted order
0

Doing that would allow one to use join to
extract fields with awk like blank handling,
and reordering support, without needing
to specify --nocheck-order.

$ printf "1 2 3\n" | join -a1 - /dev/null -o 1.3,1.1
3 1

cheers,
Pádraig.

join-null-disorder.diff
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