Finding how many lines are different between two files

Question

Write another script that uses a command pipeline to take 2 files as parameters, compare their contents and count how many lines are different. You will use wc –l to count the differing lines.

I have tried everything I can think of to do this. I have tried cmp, comm, and diff. I am not looking for a complete solution, just a push in the right direction. What command would I use for this?

Have tried every combination of tags with these.

cmp file1 file2 | wc -l

Somehow I need to edit this to work right, not necessarily using the cmp command obviously.

The way it's phrased it sounds like you're trying to get someone to do your homework... — orange, Sep 10 '13 at 02:56
because that counts the # of lines diff displays, but that is not the amount of lines that differ between the 2 files, because it includes the other lines like the one that says 2, 4c2, 4 and the one that is just ---. — user2234688, Sep 10 '13 at 02:57
I'm not asking for the answer, I want to figure it out on my own, just don't know where to look now cuz I've tried all the possibilities I could think of. — user2234688, Sep 10 '13 at 02:58

score 3 · Answer 1 · answered Mar 07 '19 at 23:33

3

I found that a side-by-side diff, suppressing context lines, is an effective method:

diff -y --suppress-common-lines file1 file2 | wc -l

answered Mar 07 '19 at 23:33

skiggety

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score 1 · Answer 2 · answered Sep 10 '13 at 03:47

1

This should do what you want

diff -U 0 file1 file2 | grep -c ^@

For example file1 contains

aaa
bbb
ccc

file2 contains

aaa
ccc
ddd

Result:

 diff -U 0 file1 file2 | grep -c ^@
 2

answered Sep 10 '13 at 03:47

cmd

11,622
7
51
61

1

It looks to me like this would count the number of differences, even if some of them are multiline, not the lines of difference. – skiggety Mar 07 '19 at 23:31

Finding how many lines are different between two files

2 Answers2