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

You can use:

diff -u f1 f2 |colordiff |diff-highlight

colordiff is a Ubuntu package. You can install it using sudo apt-get install colordiff.

diff-highlight is from git (since version 2.9). It is located in /usr/share/doc/git/contrib/diff-highlight/diff-highlight. You can put it somewhere in your $PATH.

Answer 2

Python's difflib can do this.

The documentation includes an example command-line program for you.

The exact format is not as you specified, but it would be straightforward to either parse the ndiff-style output or to modify the example program to generate your notation.

Answer 3

Most of these answers mention using of diff-highlight, a Perl module. But I didn't want to figure out how to install a Perl module. So I made a few minor changes to it to be a self-contained Perl script.

You can install it using:

▶ curl -o /usr/local/bin/DiffHighlight.pl \
   https://raw.githubusercontent.com/alexharv074/scripts/master/DiffHighlight.pl

And the usage (if you have the Ubuntu colordiff mentioned in zhanxw's answer):

▶ diff -u f1 f2 | colordiff | DiffHighlight.pl

And the usage (if you don't):

▶ diff -u f1 f2 | DiffHighlight.pl

Answer 4

I think the simpler solution is always a good solution. In my case, the below code helps me a lot. I hope it helps anybody else.

#!/bin/env python

def readfile( fileName ):
    f = open( fileName )
    c = f.read()
    f.close()
    return c

def diff( s1, s2 ):
    counter=0
    for ch1, ch2 in zip( s1, s2 ):
        if not ch1 == ch2:
            break
        counter+=1
    return counter < len( s1 ) and counter or -1

import sys

f1 = readfile( sys.argv[1] )
f2 = readfile( sys.argv[2] )
pos = diff( f1, f2 )
end = pos+200

if pos >= 0:
    print "Different at:", pos
    print ">", f1[pos:end]
    print "<", f2[pos:end]

You can compare two files with the following syntax at your favorite terminal:

$ ./diff.py fileNumber1 fileNumber2

Answer 5

If you keep your files in Git, you can diff between versions with the diff-highlight script, which will show different lines, with differences highlighted.

Unfortunately it only works when the number of lines removed matches the number of lines added - there is stub code for when lines don't match, so presumably this could be fixed in the future.

Answer 6

Git has a word diff, and defining all characters as words effectively gives you a character diff. However, newline changes are ignored.

Example

Create a repository like this:

mkdir chardifftest
cd chardifftest
git init
echo -e 'foobarbaz\ncatdog\nfox' > file
git add -A; git commit -m 1
echo -e 'fuobArbas\ncat\ndogfox' > file
git add -A; git commit -m 2

Now, do git diff --word-diff=color --word-diff-regex=. master^ master and you'll get:

Note how both additions and deletions are recognized at the character level, while both additions and deletions of newlines are ignored.

You may also want to try one of these:

git diff --word-diff=plain --word-diff-regex=. master^ master
git diff --word-diff=porcelain --word-diff-regex=. master^ master