Re: implicit redirection of background within pipeline

[Chet Ramey]

On 1/11/16 11:37 AM, Andreas Schwab wrote:
> Chet Ramey <chet.ramey@case.edu> writes:
> 
>> On 1/10/16 12:54 PM, Piotr Grzybowski wrote:
>>> hey,
>>>
>>>  I am quite sure it happens here (devel branch, at
>>> 6f82653c5ef09aeeeba4376a1c65ce86c3605c00):
>>>
>>> execute_cmd.c +5115:
>>>    if ((cmdflags & CMD_STDIN_REDIR) &&
>>>   pipe_in == NO_PIPE &&
>>>   (stdin_redirects (redirects) == 0))
>>>      async_redirect_stdin ();
>>>
>>>  but after reading the comments some 3.5k lines earlier I am not sure
>>> how to fix it; of course commenting out the if in
>>> execute_cmd.c:5112-5115 solves it, but who can tell what it breaks?
>>
>> Posix requires this behavior:
>>
>> "The standard input for an asynchronous list, before any explicit
>> redirections are performed, shall be considered to be assigned to a file
>> that has the same properties as /dev/null."
> 
> But isn't it a bug that subsequent asynchronous commands in the list are
> not redirected from /dev/null?

Yes, clearly the existing behavior is inconsistent.  My response answered
Piotr's question about what it breaks.

-- 
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, ITS, CWRU    chet@case.edu    http://cnswww.cns.cwru.edu/~chet/