tkdiff
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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.
Example usage
tkdiff <file1> <file2>
— to compare the 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 repository
tkdiff can also compare two older revisions of a file, etc.[2]