I just noticed today you can easily check file permissions by selecting the appropriate bits using an array format with a range. For example, if I want to make sure that the permissions of /etc/sudoers is 440, I could do the following:
File.stat("/etc/sudoers").mode.to_s(8)[3..5] == "440"
So, you’re converting the mode to octal format and then selecting characters 3 thur 5. Characters start at 0 from the left side of the string.