GNU bug report logs - #41001
mkdir: cannot create directory ‘test’: File exists

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Message #27 received at 41001 <at> debbugs.gnu.org (full text, mbox):

From: Jonny Grant <jg <at> jguk.org>
To: Paul Eggert <eggert <at> cs.ucla.edu>
Cc: 41001 <at> debbugs.gnu.org, Eric Blake <eblake <at> redhat.com>
Subject: Re: bug#41001: mkdir: cannot create directory ‘test’: File exists
Date: Sat, 2 May 2020 14:26:35 +0100

On 01/05/2020 21:32, Paul Eggert wrote:
> On 5/1/20 1:21 PM, Jonny Grant wrote:
>> yes, the fix pretty trivial for mkdir as you highlight EISDIR:
>> stat(), S_ISDIR(sb.st_mode), and set errno to EISDIR or output strerror(EISDIR)
> 
> That would introduce a race condition, and wouldn't behave correctly if some
> other process changes the destination from a regular file to a directory between
> the time we call mkdir and the time that we call stat.

Paul,

If developers have race conditions in their shell scripts - mkdir error 
string in the message after the colon in the output saying 
file/directory is the least of the developers' problems.

mkdir() returning EEXIST only indicates the pathname exists.

Maybe call stat() before calling mkdir() to check nothing there. It's 
more a question of doing something appropriate.

Personally I doubt POSIX will ever be updated to have more errno errors 
that distinguish between files and directories for ENOENT and EEXIST due 
to people's fears about compatibility when APIs are updated.

Cheers, Jonny

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