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On 04/14/2014 11:53 AM, Doug Hellmann wrote:
> As someone who maintains a shell-script project across several
> "sh-like" shells, I can say the edge cases cause enough work and
> testing hassles that you shouldn't undertake it lightly. Is there any
> particular need to run these tools under a non-bash shell?

I don't have one, but I've seen a few changes proposed to make the 
scripts work with other shells (although in at least one case I believe 
it was in a script explicitly using bash, so I'm not sure what the 
purpose was...).  And those edge cases are why I would like to stop 
trying to support not-bash unless someone else wants to step up and own 
that effort.

Thanks for the input.

-Ben

>
> Doug
>
> On Mon, Apr 14, 2014 at 12:26 PM, Ben Nemec <openstack at nemebean.com> wrote:
>> tldr: I propose we use bash explicitly for all diskimage-builder scripts (at
>> least for the short-term - see details below).
>>
>> This is something that was raised on my linting changes to enable set -o
>> pipefail.  That is a bash-ism, so it could break in the diskimage-builder
>> scripts that are run using /bin/sh.  Two possible fixes for that: switch to
>> /bin/bash, or don't use -o pipefail
>>
>> But I think this raises a bigger question - does diskimage-builder require
>> bash?  If so, I think we should just add a rule to enforce that /bin/bash is
>> the shell used for everything.  I know we have a bunch of bash-isms in the
>> code already, so at least in the short-term I think this is probably the way
>> to go, so we can get the benefits of things like -o pipefail and lose the
>> ambiguity we have right now.  For reference, a quick grep of the
>> diskimage-builder source shows we have 150 scripts using bash explicitly and
>> only 24 that are plain sh, so making the code truly shell-agnostic is likely
>> to be a significant amount of work.
>>
>> In the long run it might be nice to have cross-shell compatibility, but if
>> we're going to do that I think we need a couple of things: 1) Someone to do
>> the work (I don't have a particular need to run dib in not-bash, so I'm not
>> signing up for that :-) 2) Testing in other shells - obviously just changing
>> /bin/bash to /bin/sh doesn't mean we actually support anything but bash.  We
>> really need to be gating on other shells if we're going to make a
>> significant effort to support them.  It's not good to ask reviewers to try
>> to catch every bash-ism proposed in a change.  This also relates to some of
>> the unit testing work that is going on right now too - if we had better unit
>> test coverage of the scripts we would be able to do this more easily.
>>
>> Thoughts?
>>
>> Thanks.
>>
>> -Ben
>>
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