tkdiff to interactively pick files.
tkdiff<file1><file2> to compare two files.
tkdiff-conflict<file> to merge a file with conflict markers generated by "merge" or "cvs", The file is
split into two temporary files which you can then merge as usual.
tkdiff<file> to compare <file> with the most recent version checked into CVS/SCCS/RCS (checked for in
that order).
tkdiff-r<file> to compare <file> with the most recent version checked in.
tkdiff-r<rev><file> to compare <file> with revision <rev> of <file>.
tkdiff-r<rev>-r<file> to compare revision <rev> of <file> with the most recent version checked in.
tkdiff-r<rev1>-r<rev2><file> to compare revisions <rev1> and <rev2> of <file>.