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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?

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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