== Why GNU tools are sometimes not my favorite programs

Presented in the traditional illustrated form:

 ; cat a
 root
 cks
 ; cat b
 root
 cks
 abc
 ; comm -13 a b >/dev/null
 comm: file 2 is not in sorted order
 
If your _comm_ doesn't do this, don't be surprised; this behavior is new
in the very latest version of _comm_, from coreutils 7.2 (as installed
on Fedora 11; Fedora 10 didn't have it). This behavior is turned off by
the new _--nocheck-order_ option, although the manpage contains scary
warnings about this not being supported.

Congratulations, GNU coreutils maintainers. You have just broken any
number of scripts that were using _comm_ to obtain differences between
ordered files; all of these scripts now produce extra output, [[which
is bad FatalWarnings]]. Worse, fixing this will make the scripts
unportable, since not even previous versions of GNU _comm_ understand
the new _--nocheck-order_ option.

(Yes, yes, technically this behavior is allowed by the [[Single Unix
Specification ../links/SingleUnixSpecification]]. But in real life,
this is false; the true specification is not whatever is allowed by
the letter of standards, it is what everything does and what people
write to.)

Also, this is utterly the wrong way to change behavior like this.
The correct way is to first introduce the necessary command line
switches but not default to emitting a warning, with a note that
in X amount of time the default will change. Then several versions
later you can start to think about changing the default, since people
have had a chance to add the new options to their scripts. (You will
still fail, because people don't even look at perfectly working
scripts, much less update them, but at least you will have made vague
motions towards doing the right thing instead of being an [[asshole
http://diveintomark.org/archives/2004/08/16/specs]].)