GNU Diffutils is a package of several programs related to finding differences
between files, including four utilities: diff, cmp, diff3 and sdiff. Diff
compares and shows the differences between two files line by line. Cmp
shows the offset and line numbers where two files differ, or
cmp can show the characters that differ between the two files.
Diff3 shows the differences between three files. Sdiff
can be used to merge two files interactively.