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When I use diff -y to compare two text files with long lines of text, the result cuts off each column and I cannot read an entire line. I would like instead the text to wrap (or fold as it is also called) so that I can read the whole line.

For example, say I have two simple text files one line each:

cat tmp.txt tmp2.txt
The quick brown fox jumped over the lazy dog. This line is very long and will not show when I use a diff. 
The quick brown fox did not jump over the lazy dog. This line is very long and will not show when I use a diff. 

diffing them I get,

diff -y tmp.txt tmp2.txt
The quick brown fox jumped over the lazy dog. This line is ve | The quick brown fox did not jump over the lazy dog. This line

which cuts off the lines in the middle.

I know about the -W option to make it wider, but the lines are longer than my screen width so this does not help. Using a simple diff does make the text wrap, but there is no text wrapping with diff -y.

So how can I use diff -y with text wrapping?

I'm using the terminal on a Mac, if that helps.

This seems like a simple thing to want, but after searching everywhere I cannot find a solution!

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  • 1
    "I'm using the terminal on a Mac" and yet this is tagged "Linux"
    – muru
    Aug 26, 2019 at 4:39
  • if it is ok to lose original line numbers, if you just want to see the visual diff ?
    – amisax
    Aug 26, 2019 at 5:13

3 Answers 3

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If it is ok to lose line number information , and you are just interested in visual diffs, you could fold the files first before diffing them.

diff -y <(fold -s -w72 file1) <(fold -s -w72 file2) -W 200

In this command we have used process substitution to first fold each file to line of 72 characters, but with -s option we ensure that the lines are broken only on the space character.

Once the lines are wrapped by fold, diff command would work on the wrapped output.

EDIT: specifying -W to diff with a larger value than that given in the fold will ensure that the diff and fold have sufficient space to work with each other. In this case -W 200 is given to diff

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    Please also consider expanding width of diff command with -W option. It seemed handy when used along with your answer ,example: diff -y <(fold -s -w72 file1) <(fold -s -w72 file2) -W 200. Not all lines were folded properly with just diff -y <(fold -s -w72 file1) <(fold -s -w72 file2). Also not all line were wrapped properly with just diff -y <(fold -s -w72 file1) <(fold -s -w72 file2) -W 200.
    – ss_iwe
    Aug 26, 2019 at 6:04
  • Thank you so much! This works perfectly!
    – xenkan
    Sep 12, 2019 at 21:38
  • Glad it worked for you. Do mark this the accepted answer in that case.
    – amisax
    Sep 13, 2019 at 10:35
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I like to use icdiff for this task.

The screenshot after running icdiff tmp.txt tmp1.txt:

icdiff outputs

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  • vimdiff is my prefrence Dec 15, 2019 at 5:43
  • Icdiff works to some degree, but if lines on the right are longer than those on the left, just a newline is inserted so that the end of the right-hand line appears on the left. Very confusing. Jul 21, 2021 at 7:16
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Kdiff3 has a setting Diffview > Word Wrap Diff Windows which breaks lines at the closest word boundary in the frame. It is the only tool I have found that does this.

kdiff3 showing diff of two texts with word wrap

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