My version of sort seems to have unpredictable behavior, based on the data
being sorted:

$ sort <foo
t
te
tec

$ sort <foo
t.co
tec.co
te.co

$ sort <foo
t.c
te.c
tec.c

$ sort <foo
t.co
tec.co
te.co

$ sort <foo
tec.o
te.o
t.o


$ sort --version
sort (GNU coreutils) 8.4
Copyright (C) 2010 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html
>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Written by Mike Haertel and Paul Eggert.
-- 

Using flags -d, -n, -R, -r, and -i had no effect on this behavior.

*Mike Bartman*
*senior software engineer - platform*

*tel* (415)-578-5222 x492
*email *michael.bartman@sparkpost.com