# Automatic Diff -q Between Two Directories

**URL:** <https://www.ruby-forum.com/t/automatic-diff-q-between-two-directories/194665>\
**Category:** Ruby\
**Created:** [September 8, 2010, 7:59pm UTC](https://www.ruby-forum.com/t/automatic-diff-q-between-two-directories/194665 "2010-09-08T19:59:10Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![ric](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/c77e96/32.png) [@ric](https://www.ruby-forum.com/u/ric)\
**Post date:** [September 8, 2010, 7:59pm UTC](https://www.ruby-forum.com/t/automatic-diff-q-between-two-directories/194665/1 "2010-09-08T19:59:10Z")

</div>

Greetings:  
I’ve been toying with ruby off/on in years. Now I’ve come across a  
practical application that ruby may be of use to me.

Scenario: Two directories with many files in parallel: differences is  
content, names are same.

I need to check which files have been modified.  
That is, automating the $diff -q command thusly:

[/Users/admin/workarea]diff -q file1.txt file2.txt \>\> result.txt  
[/Users/admin/workarea]diff -q file3.txt file4.txt \>\> result.txt  
…

[/Users/admin/workarea]more result.txt  
Files file1.txt and file2.txt differ  
Files file3.txt and file4.txt differ  
…

So imaging the scenario:  
/src1  
/src1/file1.txt  
/src1/file2.txt  
…

vs.

/src2  
/src2/file1.txt  
/src2/file2.txt  
…

So essentially there’s a loop through one directory vs a parallel  
directory.  
Is there simple example how I could do this in (interactive/irb) Ruby?

Regards,  
Ric.

---

<div class="post-metadata">

**Author:** ![ric](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/c77e96/32.png) [@ric](https://www.ruby-forum.com/u/ric)\
**Post date:** [September 8, 2010, 11:07pm UTC](https://www.ruby-forum.com/t/automatic-diff-q-between-two-directories/194665/2 "2010-09-08T23:07:21Z")

</div>

On Sep 8, 2010, at 10:59 , Frederick L. wrote:

> Scenario: Two directories with many files in parallel: differences is  
> content, names are same.

% man diff  
…  
-r --recursive  
Recursively compare any subdirectories found.  
…

---

<div class="post-metadata">

**Author:** ![ric](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/c77e96/32.png) [@ric](https://www.ruby-forum.com/u/ric)\
**Post date:** [September 9, 2010, 1:07am UTC](https://www.ruby-forum.com/t/automatic-diff-q-between-two-directories/194665/3 "2010-09-09T01:07:56Z")

</div>

Ryan D. wrote:

> On Sep 8, 2010, at 10:59 , Frederick L. wrote:
> 
> > Scenario: Two directories with many files in parallel: differences is  
> > content, names are same.
> 
> % man diff  
> …  
> -r --recursive  
> Recursively compare any subdirectories found.  
> …

Did the man diff -rq /dir1 /dir2 \> result.txt

Works great!  
So simple, so useful.  
Thanks!