comparing two files in perl

john83reuben · 10-09-2009, 03:02 PM

Hi All,

I would like to ask opinion from perl experts.

I want to compare 2 files and show the differences in a text file.

For example, if i open File A an B in notepad

File A:
apple orange grape
apple orange grape kiwi
apple orange grape kiwi melon pineapple
orange grape kiwi pineapple
apple orange grape kiwi melon pineapple
apple orange grape kiwi

File B:
apple orange grape
apple orange grape kiwi
orange grape kiwi pineapple
apple orange grape kiwi melon pineapple
apple orange grape kiwi

Quote:

line3 is missing in File B

So if I did a File compare (line by line),
the differences will be in line3, line4, line5, line 6.

But I dont want it to be like that.

I want it to be like this

Quote:

line1: no differences
line2: no differences
line3: differences detected. Line 3 is missing from File B
line4: no differences
line5: no differences
line6: no differences

Can Text:: Diff able to perform the work.

Please advice.

John

neonsignal · 10-09-2009, 05:37 PM

You won't get exactly the output you want without some work manipulating the results from Text::Diff, but it will do a line by line match similar to diff

Code:

use Text::Diff;
print diff "t1.txt", "t2.txt", { STYLE => "Unified" };

will produce

Code:

--- t1.txt	Sat Oct 10 09:15:35 2009
+++ t2.txt	Sat Oct 10 09:15:44 2009
@@ -1,6 +1,5 @@
 apple orange grape 
 apple orange grape kiwi
-apple orange grape kiwi melon pineapple
 orange grape kiwi pineapple
 apple orange grape kiwi melon pineapple
 apple orange grape kiwi

There are also a few other styles of output.

You should be wary of using it on very large files.