GNU bug report logs - #72274
diff: option to ignore leading white space

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

From: Vincent Lefevre <vincent <at> vinc17.net>
To: bug-diffutils <at> gnu.org
Subject: option to ignore leading white space
Date: Wed, 24 Jul 2024 13:59:33 +0200

There should be an option to ignore leading white space, like
there is one for trailing white space, and it should probably
be integrated in the -b option.

Basically, I'd like to be able to get only lines that differ by words.

Currently:

cventin:~> diff -bu <(printf "ab cd\n") <(printf " ab  cd \n")
--- /proc/self/fd/11    2024-07-24 13:58:43.515131625 +0200
+++ /proc/self/fd/14    2024-07-24 13:58:43.515131625 +0200
@@ -1 +1 @@
-ab cd
+ ab  cd 

-- 
Vincent Lefèvre <vincent <at> vinc17.net> - Web: <https://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)

Message #12 received at 72274 <at> debbugs.gnu.org (full text, mbox):

From: Eric Deplagne <eric <at> deplagne.name>
To: Vincent Lefevre <vincent <at> vinc17.net>
Cc: 72274 <at> debbugs.gnu.org
Subject: Re: [bug-diffutils] bug#72274: option to ignore leading white space
Date: Wed, 24 Jul 2024 21:47:02 +0200

  diff -w might be your friend.

  $ diff -wus <(printf "ab cd\n") <(printf " ab  cd \n")
  Les fichiers /dev/fd/63 et /dev/fd/62 sont identiques

On 2024-07-24 13:59, Vincent Lefevre wrote:
> There should be an option to ignore leading white space, like
> there is one for trailing white space, and it should probably
> be integrated in the -b option.
> 
> Basically, I'd like to be able to get only lines that differ by words.
> 
> Currently:
> 
> cventin:~> diff -bu <(printf "ab cd\n") <(printf " ab  cd \n")
> --- /proc/self/fd/11    2024-07-24 13:58:43.515131625 +0200
> +++ /proc/self/fd/14    2024-07-24 13:58:43.515131625 +0200
> @@ -1 +1 @@
> -ab cd
> + ab  cd

-- 
  Eric Deplagne

Message #15 received at 72274 <at> debbugs.gnu.org (full text, mbox):

From: Vincent Lefevre <vincent <at> vinc17.net>
To: Eric Deplagne <eric <at> deplagne.name>
Cc: 72274 <at> debbugs.gnu.org
Subject: Re: [bug-diffutils] bug#72274: option to ignore leading white space
Date: Wed, 24 Jul 2024 22:21:50 +0200

On 2024-07-24 21:47:02 +0200, Eric Deplagne wrote:
>   diff -w might be your friend.
> 
>   $ diff -wus <(printf "ab cd\n") <(printf " ab  cd \n")
>   Les fichiers /dev/fd/63 et /dev/fd/62 sont identiques

But this one is wrong:

$ diff -wus <(printf "ab cd\n") <(printf " abcd \n")
Files /proc/self/fd/11 and /proc/self/fd/14 are identical

-- 
Vincent Lefèvre <vincent <at> vinc17.net> - Web: <https://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)

Message #18 received at 72274 <at> debbugs.gnu.org (full text, mbox):

From: Eric Deplagne <eric <at> deplagne.name>
To: Vincent Lefevre <vincent <at> vinc17.net>
Cc: 72274 <at> debbugs.gnu.org
Subject: Re: [bug-diffutils] bug#72274: option to ignore leading white space
Date: Wed, 24 Jul 2024 23:15:27 +0200

On 2024-07-24 22:21, Vincent Lefevre wrote:
> On 2024-07-24 21:47:02 +0200, Eric Deplagne wrote:
>>   diff -w might be your friend.
>> 
>>   $ diff -wus <(printf "ab cd\n") <(printf " ab  cd \n")
>>   Les fichiers /dev/fd/63 et /dev/fd/62 sont identiques
> 
> But this one is wrong:
> 
> $ diff -wus <(printf "ab cd\n") <(printf " abcd \n")
> Files /proc/self/fd/11 and /proc/self/fd/14 are identical

  Wrong, indeed. :/

-- 
  Eric Deplagne

Message #21 received at 72274 <at> debbugs.gnu.org (full text, mbox):

From: Tim Chase <debian <at> tim.thechases.com>
To: Vincent Lefevre <vincent <at> vinc17.net>
Cc: 72274 <at> debbugs.gnu.org, Eric Deplagne <eric <at> deplagne.name>
Subject: Re: [bug-diffutils] bug#72274: option to ignore leading white space
Date: Wed, 24 Jul 2024 16:57:49 -0500

On 2024-07-24 22:21, Vincent Lefevre wrote:
> $ diff -wus <(printf "ab cd\n") <(printf " abcd \n")
> Files /proc/self/fd/11 and /proc/self/fd/14 are identical

Doesn't even require the leading/trailing space:

 $ echo abcd > nospace
 $ echo ab cd > space
 $ diff -wus nospace space
 Files nospace and space are identical

FWIW, this happens with diff(1) on FreeBSD & OpenBSD too, so it's
not just a GNU diff(1) thing.

-tkc

Message #24 received at 72274 <at> debbugs.gnu.org (full text, mbox):

From: Vincent Lefevre <vincent <at> vinc17.net>
To: Tim Chase <debian <at> tim.thechases.com>
Cc: 72274 <at> debbugs.gnu.org, Eric Deplagne <eric <at> deplagne.name>
Subject: Re: [bug-diffutils] bug#72274: option to ignore leading white space
Date: Thu, 25 Jul 2024 02:42:16 +0200

On 2024-07-24 16:57:49 -0500, Tim Chase wrote:
> On 2024-07-24 22:21, Vincent Lefevre wrote:
> > $ diff -wus <(printf "ab cd\n") <(printf " abcd \n")
> > Files /proc/self/fd/11 and /proc/self/fd/14 are identical
> 
> Doesn't even require the leading/trailing space:
> 
>  $ echo abcd > nospace
>  $ echo ab cd > space
>  $ diff -wus nospace space
>  Files nospace and space are identical
> 
> FWIW, this happens with diff(1) on FreeBSD & OpenBSD too, so it's
> not just a GNU diff(1) thing.

That's why -w is not the right option.

Contents that have been passed through HTML often get all their
leading white space removed. Hence the usefulness of an option
to ignore leading white space.

-- 
Vincent Lefèvre <vincent <at> vinc17.net> - Web: <https://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)

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