Please note that this software is not "open source", but the source is available for use and modification by individuals, non-profit organizations, and worker-owned businesses (see the license section below for details).
This is just a bag of stuff. The first thing I've added is a tool for merging sorted files. For example, this command:
$ time target/release/merge a.csv b.csv | wc
12710167 12710167 1591781524
real 0m10.963s
user 0m14.925s
sys 0m5.488s...should be equivalent to this one:
$ export LC_ALL=C
$ time sort a.csv b.csv | uniq | wc
12710167 12710167 1591781524
real 0m14.645s
user 0m19.738s
sys 0m3.914s...except slightly faster and with a much smaller memory footprint.
This software is published under the Anti-Capitalist Software License (v. 1.4).