Date: Wed, 27 May 2020 12:52:22 +0300 From: Yuri Pankov <ypankov@fastmail.com> To: Fehmi Noyan ISI <fnoyanisi@yahoo.com>, Baptiste Daroussin <bapt@FreeBSD.org> Cc: freebsd-hackers@freebsd.org Subject: Re: diff(1) -N behaviour - Bug 233402 Message-ID: <b4385df3-5698-03a2-256d-d77b1a8a91fb@fastmail.com> In-Reply-To: <AFA8A27C-D6DC-4B45-9FDC-9D396EE7A268@yahoo.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> <0E0FB885-5D64-41F1-9A8B-8CEDB5884762@yahoo.com> <20200527090652.dubjpd2y2n5yfbta@ivaldir.net> <AFA8A27C-D6DC-4B45-9FDC-9D396EE7A268@yahoo.com>
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Fehmi Noyan ISI via freebsd-hackers wrote: > > >> On 27/05/2020, at 9:06 PM, Baptiste Daroussin <bapt@FreeBSD.org> wrote: >> >> On Wed, May 27, 2020 at 08:52:38PM +1200, Fehmi Noyan ISI via freebsd-hackers wrote: >>> >>> >>>> On 23/05/2020, at 11:47 PM, Yuri Pankov <ypankov@fastmail.com> wrote: >>>> >>>> Fehmi Noyan ISI via freebsd-hackers wrote: >>>>>> On 23/05/2020, at 11:21 PM, Yuri Pankov <ypankov@fastmail.com> wrote: >>>>>> >>>>>> 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’s 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 >>>>>> >>>>>> I think both descriptions say the same, i.e. "zero size" == "empty”? >>>>> Maybe it’s my interpretation, but if you do not supply the second argument to diff(1), it complains >>>>> $ echo “test” > 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 “test” > a.txt >>>>> $ diff -N a.txt nofile >>>>> 1d0 >>>>> < test >>>>> $ >>>> >>>> I must admit that I never used -N without -r, so it's probably the only case that needs fixing? >>>> >>>> $ 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 >>>> >>> >>> Took me a while to reply… >>> 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? >>> >> Yes we do, if you do provide a patch I would be more than happy to review and >> apply it. >> >> Best regards, >> Bapt > > Cheers… > > I will be working on it and update bug 233402 Great! I wasn't discouraging you, rather trying to understand what case exactly we are talking about. Also, I think the -N option description in the man page should look more like GNU's one, as currently (I think) it implies that -r is used and we are comparing directories recursively.
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