Kaleidoscope's ksdiff command-line tool lets you compare and merge any number of files from the Terminal. To install or remove, follow these instructions:
Usage Examples
Compare the text content two draft plain text documents with the final Word document:
Merge conflicting changes between Draft1.txt and Draft2.txt into Merge.txt:
Pipe content into ksdiff using -. This command will compare an original LoremIpsum.txt file with one where all u characters have been replaced wirth v.
Repeatedly send content into the same Kaleidoscope window using the -l option (and piping). The following command will show processes that consume at least 1% of CPU. Use multiple times to compare over time.