Re: Script broken after updating bash to 4.3.46-7?

[cyg Simple <cygsimple@gmail.com>]

On 8/30/2016 1:38 PM, Eric Blake wrote:
> On 08/30/2016 12:04 PM, cyg Simple wrote:
>> On 8/29/2016 2:30 PM, Eric Blake wrote:
>>>
>>> Simplest fix:
>>>
>>> read ... < <(mysql ... | dos2unix)
>>>
>>
>> This will break when the data returned by mysql is supposed to contain \r.
>>
>>> There. Now you aren't feeding \r to read in the first place.
>>>
>>
>> But you might want to feed \r to read.  It isn't a fix, it is a
>> potential work around dependent on the data set results.  If a read that
>> is supposed to be reading binary data doesn't pass all of the data to
>> the routine then it is broken.
> 
> Now we're talking past each other.
> 
> That's what the recent bash fixed.  'read' in bash 3.2.42-4 was broken -
> it corrupted binary data, with no recourse, by eating \r (and worse, by
> sometimes eating the byte after \r).  'read' in bash 3.2.46-7 is fixed -
> by default it is strictly binary (all bytes are read as-is, including
> \r), but can also be switched to text mode (using 'igncr', all \r are
> ignored).  If you want to preserve mid-line \r but treat line endings of
> \r\n as a single byte, then leave binary mode on and strip the line
> endings via a separate tool like d2u (note, however, that it is very
> rare to have data where mid-line \r is important but line-ending \r\n
> should be treated as plain \n).
> 
> I strongly think that using igncr is a crutch, and you normally
> shouldn't use it; particularly not if you want to be portable to other
> platforms.  Instead, massaging your data through d2u is a great way to
> be portable.  But sometimes the ease of ignoring ALL \r is easier than
> worrying about portability, so I keep the 'igncr' code in Cygwin.
> 
> And it is only because the OP tried using 'igncr' in the first place
> (whether or not it was actually needed) that we have now flushed out the
> existence of a latent bug in the 'igncr' implementation that interacts
> weirdly with $()\n in PS1.  On that front, I'm still hoping to find time
> to debug and/or for someone to post a patch.  But whether PS1 behaves
> weirdly under 'igncr' is orthogonal to my suggestion above - using
> 'mysql|d2u' is a great way to avoid the need to worry about 'igncr'.
> 

Thank you for the retort Eric.  Happy to know that it is fixed which in
the back of my mind I knew already.  I can imagine data such as full
message email or a small document data containing \r\n as valid data in
the database field and if you use a line ending conversion utility you
might loose that data.

-- 
cyg Simple

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