Using 'diff' (or anything else) to get character-level diff between text files

Question

I\'d like to use \'diff\' to get a both line difference between and character difference. For example, consider:

File 1

abcde
ab         


        

Answer 1

Coloured, character-level diff ouput

Here's what you can do with the the below script and diff-highlight (which is part of git):

#!/bin/sh -eu

# Use diff-highlight to show word-level differences

diff -U3 --minimal "$@" |
  sed 's/^-/\x1b[1;31m-/;s/^+/\x1b[1;32m+/;s/^@/\x1b[1;34m@/;s/$/\x1b[0m/' |
  diff-highlight

_{(Credit to @retracile's answer for the sed highlighting)}

Answer 2

Python has convenient library named difflib which might help answer your question.

Below are two oneliners using difflib for different python versions.

python3 -c 'import difflib, sys; \
  print("".join( \
    difflib.ndiff( \ 
      open(sys.argv[1]).readlines(),open(sys.argv[2]).readlines())))'
python2 -c 'import difflib, sys; \
  print "".join( \
    difflib.ndiff( \
      open(sys.argv[1]).readlines(), open(sys.argv[2]).readlines()))'

These might come in handy as a shell alias which is easier to move around with your .${SHELL_NAME}rc.

$ alias char_diff="python2 -c 'import difflib, sys; print \"\".join(difflib.ndiff(open(sys.argv[1]).readlines(), open(sys.argv[2]).readlines()))'"
$ char_diff old_file new_file

And more readable version to put in a standalone file.

#!/usr/bin/env python2
from __future__ import with_statement

import difflib
import sys

with open(sys.argv[1]) as old_f, open(sys.argv[2]) as new_f:
    old_lines, new_lines = old_f.readlines(), new_f.readlines()
diff = difflib.ndiff(old_lines, new_lines)
print ''.join(diff)

Answer 3

cmp -l file1 file2 | wc

Worked well for me. The leftmost number of the result indicates the number of characters that differ.