Using the DIFF Command for Natural Language Processing
  Diff is a software program that detects differences between two data sets and is useful in natural language processing. This paper shows several examples of the application of diff. They include the detection of differences between two different datasets, extraction of rewriting rules, merging of two different datasets, and the optimal matching of two different data sets. Since diff comes with any standard UNIX system, it is readily available and very easy to use. Our studies showed that diff is a practical tool for research into natural language processing. 
Masaki Murata and Hitoshi Isahara