By placing a group of characters within brackets ( \[ and \] ), you can specify that the character at that position can be any one character found within the bracket group. For example, to find the lines that contain too or two , you would specify those variations succinctly by using the following pattern: grep "t[wo]o" GPL-3 The output shows that both variations exist in the file: Output your programs, too . freedoms that you received. You must make sure that they, too , receive Developers that use the GNU GPL protect your rights with two steps: a computer ne two rk, with no transfer of a copy, is not conveying. System Libraries, or general-purpose too ls or generally available free Corresponding Source from a ne two rk server at no charge. ... ... Bracket notation gives you some interesting options. You can have the pattern match anything except the characters within a bracket by beginning the list of characters within the brackets with a ^ character...