GNU bug report logs - #25223
chmod +w does not work

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

From: Eugen Dedu <eugen.dedu <at> univ-fcomte.fr>
To: bug-coreutils <at> gnu.org
Subject: chmod +w does not work
Date: Sun, 18 Dec 2016 13:37:06 +0100

Hi,

chmod +w file does not work:

snoopy:~$ touch ff
snoopy:~$ ls -l ff
-rw-r--r-- 1 ededu ededu 0 Dec 18 13:31 ff
snoopy:~$ chmod +w ff
snoopy:~$ ls -l ff
-rw-r--r-- 1 ededu ededu 0 Dec 18 13:31 ff
snoopy:~$ chmod +x ff
snoopy:~$ ls -l ff
-rwxr-xr-x 1 ededu ededu 0 Dec 18 13:31 ff
snoopy:~$ chmod --version
chmod (GNU coreutils) 8.26

Kind regards,
-- 
Eugen

Message #8 received at 25223 <at> debbugs.gnu.org (full text, mbox):

From: Pádraig Brady <P <at> draigBrady.com>
To: Eugen Dedu <eugen.dedu <at> univ-fcomte.fr>, 25223 <at> debbugs.gnu.org
Subject: Re: bug#25223: chmod +w does not work
Date: Sun, 18 Dec 2016 17:34:22 +0000

tag 25223 notabug
close 25223
stop

On 18/12/16 12:37, Eugen Dedu wrote:
> Hi,
> 
> chmod +w file does not work:
> 
> snoopy:~$ touch ff
> snoopy:~$ ls -l ff
> -rw-r--r-- 1 ededu ededu 0 Dec 18 13:31 ff
> snoopy:~$ chmod +w ff
> snoopy:~$ ls -l ff
> -rw-r--r-- 1 ededu ededu 0 Dec 18 13:31 ff
> snoopy:~$ chmod +x ff
> snoopy:~$ ls -l ff
> -rwxr-xr-x 1 ededu ededu 0 Dec 18 13:31 ff
> snoopy:~$ chmod --version
> chmod (GNU coreutils) 8.26

From the man page, taking particular note of the last line...

"A  combination  of the letters ugoa controls which users' access to the
file will be changed: the user who owns it  (u),  other  users  in  the
file's group (g), other users not in the file's group (o), or all users
(a).  If none of these are given, the effect is as if (a)  were  given,
but bits that are set in the umask are not affected."

Message #11 received at 25223 <at> debbugs.gnu.org (full text, mbox):

From: Eugen Dedu <eugen.dedu <at> univ-fcomte.fr>
To: Pádraig Brady <P <at> draigBrady.com>, 25223 <at> debbugs.gnu.org
Subject: Re: bug#25223: chmod +w does not work
Date: Sun, 18 Dec 2016 18:45:43 +0100

On 18/12/16 18:34, Pádraig Brady wrote:
> tag 25223 notabug
> close 25223
> stop
>
> On 18/12/16 12:37, Eugen Dedu wrote:
>> Hi,
>>
>> chmod +w file does not work:
>>
>> snoopy:~$ touch ff
>> snoopy:~$ ls -l ff
>> -rw-r--r-- 1 ededu ededu 0 Dec 18 13:31 ff
>> snoopy:~$ chmod +w ff
>> snoopy:~$ ls -l ff
>> -rw-r--r-- 1 ededu ededu 0 Dec 18 13:31 ff
>> snoopy:~$ chmod +x ff
>> snoopy:~$ ls -l ff
>> -rwxr-xr-x 1 ededu ededu 0 Dec 18 13:31 ff
>> snoopy:~$ chmod --version
>> chmod (GNU coreutils) 8.26
>
>>From the man page, taking particular note of the last line...
>
> "A  combination  of the letters ugoa controls which users' access to the
> file will be changed: the user who owns it  (u),  other  users  in  the
> file's group (g), other users not in the file's group (o), or all users
> (a).  If none of these are given, the effect is as if (a)  were  given,
> but bits that are set in the umask are not affected."

Ah, I see now (I have read the man without paying particular attention 
to that line).

I wonder why I have not seen this particularity until now; I looked back 
at version 5.2.1 and this line in the man page was still there...  Is 
there a rationale for this, i.e. chmod to use umask?

Thank you,
-- 
Eugen

Message #14 received at 25223 <at> debbugs.gnu.org (full text, mbox):

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Eugen Dedu <eugen.dedu <at> univ-fcomte.fr>, Pádraig Brady
 <P <at> draigBrady.com>, 25223 <at> debbugs.gnu.org
Subject: Re: bug#25223: chmod +w does not work
Date: Sun, 18 Dec 2016 11:15:21 -0800

Eugen Dedu wrote:
> Is there a rationale for this, i.e. chmod to use umask?

It's specified by POSIX. I expect the idea was to make it a bit harder to grant 
permissions that the user didn't intend.

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