# File lib/bat.rb, line 348
    def avail_n_single(file)
        avail = false
        if (fs = Dir.glob(file)).count == 1
            file = fs[0]
        elsif not fs or fs.count == 0
            wrn "#{file} not available :-("
            file = nil
        else
            p fs
            err "Too many versions of #{file} available (expected one)!"
        end
        return file
    end