"A few years back, when a user at the University of Manchester asked for help with the ‘diff – files too big/ out of memory’ problem, I wrote a modern version that I called idiffh (for Ian’s diffh). My ground rules were:<br />
Work on any text files on any operating system with a C compilerHave no limits on, e.g., line lengths or file sizeNever ‘give up’ if the going gets tough (i.e. when the files are very different)"

something to try