void logFile(string srcdir, string src, string destdir, string dest)
{
    chdir(g_cwd);
    md(destdir);

    // copy srdir/src to destdir/dest, where destdir also contains the
    // topic-icentifier (e.g., b in tmp/install/b)

    run("cp " + srcdir + "/" + src + " " + destdir + "/" + dest);
}
