Yes, your regexp pattern is wrong. [0-255] does not match litterally the characters 0,1,2 through 255, but instead 0 thourgh 2 and 5, which is 3 characters.

There are regexes out there that will only match a valid ip, but they are at least 5 lines long and really fairly ugly. Since you know the lsattr command is never going to return an invalid ip address, your best bet is to just construct a regex that matches things resembeling an IP, for exampe: /\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}/