atc is a small, simple program to wait until the end of a second before exiting. It might be useful for aligning clocks, such that you only have to say, "execute every second" instead of doing it yourself. To install from a tarball, you can do the standard GNU autoconf './configure && make && make install' procedure. If you're installing from the Git repository, you'll need to run `autoreconf --install' first to generate the necessary files.