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bug#14152: [PATCH] build: use 'chmod a-w' instead of 'chmod -w'
From: |
Eric Blake |
Subject: |
bug#14152: [PATCH] build: use 'chmod a-w' instead of 'chmod -w' |
Date: |
Mon, 08 Apr 2013 08:09:05 -0600 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130402 Thunderbird/17.0.5 |
On 04/06/2013 04:27 PM, Bob Proulx wrote:
> Pádraig Brady wrote:
>>> - && chmod -w address@hidden
>>> \
>>> + && chmod a-w address@hidden
>>> \
>>
>> I'll apply that fix.
>
> I think it is always a good idea to use 'a' when there isn't any other
> specific reason to do anything different. Or put the reverse way,
> whenever I see a naken "-[rwx]" then I am suspicious of the action.
> Because it masks with umask and is almost never what is desired.
Actually, POSIX says that:
chmod -w foo
is undefined (that is, an argument with a leading - is interpreted as an
option rather than as a mode string, but chmod is NOT required to
support a -w option, even though many implementations support it as an
extension). Meanwhile, POSIX requires that
chmod -- -w foo
is required to mask with umask. In fact, in coreutils, we exploit the
fact that chmod -[rwx] is undefined, in order to emit warnings if the
resulting change did not disable all bits. Using a-w instead of the
undefined '-w' or the well-defined but confusing '-- -w' is indeed the
right way to fix things.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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