I just installed a physics simulation package in OSX, one that I have installed and used on several other occasions. For some reason this time my username was not added to any of the write permissions for any of the directories or files. The only way that I know of to add myself is right clicking on every file selecting get info and then adding myself in the user list. Is there a better way to do this or execute it from the command line so that I can change every file and directory/subdirectory to read/write for my user?