GNU bug report logs - #79775
Use a program to define line-wise (not file-wise) comparison

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Carl Ponder <cponder <at> nvidia.com>
To: <submit <at> debbugs.gnu.org>
Subject: Use a program to define line-wise (not file-wise) comparison
Date: Wed, 5 Nov 2025 17:21:28 -0600

Package: diffutils
Version: 1:3.10-1build1
Severity: wishlist

This form allows me to use a program to compare 2 files and use sdiff to 
format the results:

sdiff --diff-program=PROGRAM ...

What I *really* want to do is define my own line-wise comparison, 
though, so "sdiff" will show lines as matching if the approximately 
match in a way I specify.
Allowing me to pass positional arguments to the comparator would give me 
flexibility without having to write a unique comparator program for each 
case.
Here are two examples:

sdiff --comparator-program=prefix --comparator-arg="5" ...
sdiff --comparator-program=field --comparator-arg='\d+ (\d+) .*' 
--comparator-arg='\d+ \d+ (\d+) .*' ...

The first case would match the first 5 characters of each line. The 
second case would match numbers in the second column of the first line 
with the third column of the second line.
Note that "sdiff" doesn't have to process these arguments, it just 
passes them verbatim as positional-parameters to the comparator program, 
along with the 2 lines being compared.
The comparator programs would just be executables, written any way 
that's convenient.

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