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Date:      Wed, 27 May 2020 20:52:38 +1200
From:      Fehmi Noyan ISI <fnoyanisi@yahoo.com>
To:        Yuri Pankov <ypankov@fastmail.com>
Cc:        freebsd-hackers@freebsd.org
Subject:   Re: diff(1) -N behaviour - Bug 233402
Message-ID:  <0E0FB885-5D64-41F1-9A8B-8CEDB5884762@yahoo.com>
In-Reply-To: <efe1c596-f99e-5e1e-3c1a-0e4af38e3464@fastmail.com>
References:  <B380BAF4-2343-4A22-A26D-13437ECC00C2.ref@yahoo.com> <B380BAF4-2343-4A22-A26D-13437ECC00C2@yahoo.com> <94a82a22-b5c9-b797-30cc-0242f6da1c8a@fastmail.com> <4ADEBC26-0F93-45C1-B775-E6E33E95FDC1@yahoo.com> <efe1c596-f99e-5e1e-3c1a-0e4af38e3464@fastmail.com>

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> On 23/05/2020, at 11:47 PM, Yuri Pankov <ypankov@fastmail.com> wrote:
>=20
> Fehmi Noyan ISI via freebsd-hackers wrote:
>>> On 23/05/2020, at 11:21 PM, Yuri Pankov <ypankov@fastmail.com> =
wrote:
>>>=20
>>> Fehmi Noyan ISI via freebsd-hackers wrote:
>>>> Hiya
>>>> Apparently, after we switched from GNU diff to BSD diff, the -N =
flag no longer assumes absent files as empty.
>>>> There is a bug report about GNU diff compatibility but when I look =
at diff(1) man page, I see that not treating absent files as empty is =
intentional rather than a missing functionality.
>>>> If this is not the case, I can work on patch to match to GNU diff =
behaviour, otherwise, this bug report can be closed I think.
>>>> What=E2=80=99s your take on this?
>>>> -N --new-file
>>>>     If a file is found in only one directory, act as if it was =
found
>>>>     in the other directory too but was of zero size.
>>>> man for GNU diff
>>>> -N, --new-file
>>>>     treat absent files as empty
>>>=20
>>> I think both descriptions say the same, i.e. "zero size" =3D=3D =
"empty=E2=80=9D?
>> Maybe it=E2=80=99s my interpretation, but if you do not supply the =
second argument to diff(1), it complains
>> $ echo =E2=80=9Ctest=E2=80=9D > a.txt
>> $ diff -N a.txt nofile
>> diff: nofile: No such file or directory
>> $
>> GNU diff assumes an empty file for the missing second file and makes =
the comparison
>> $ echo =E2=80=9Ctest=E2=80=9D > a.txt
>> $ diff -N a.txt nofile
>> 1d0
>> < test
>> $
>=20
> I must admit that I never used -N without -r, so it's probably the =
only case that needs fixing?
>=20
> $ mkdir a b
> $ echo bar > a/foo
> $ diff -ruN a b
> diff -ruN a/foo b/foo
> --- a/foo       2020-05-23 14:44:34.525932000 +0300
> +++ b/foo       1970-01-01 03:00:00.000000000 +0300
> @@ -1 +0,0 @@
> -bar
>=20

Took me a while to reply=E2=80=A6
With -N, GNU diff does not give an ENOENT

% echo foo > bar
% diff bar nofile.txt
diff: nofile.txt no such file or directory
% diff -N bar nofile.txt
1d0
< foo

Do we want BSD diff do the same, i.e. match the -N functionality of GNU =
diff?

Fehmi








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