tkdiff is a graphical diff viewer based on the Tk framework.[1] It is capable of inter-operating with source-control systems like CVS and Subversion to show the differences between the local copy and the repository version. Such a line-by-line comparison is often considered to be good software engineering practice before committing code changes.
tkdiff <file1> <file2> — to compare the two files <file1> and <file2>tkdiff <file> — to compare the local version of the given file to the most recent version in the CVS/Subversion repositorytkdiff can also compare two older revisions of a file, etc.[2]