Samba and ShellCheck

[Martin Schwenke]

Hi Andreas,

On Tue, 23 Aug 2022 07:50:24 +0200, Andreas Schneider via
samba-technical <samba-technical at lists.samba.org> wrote:

> for Samba master we have ShellCheck with error level in place now. It will 
> check that our scripts are error free!

Yay!

That probably isn't true for CTDB, but we are gradually improving things.

> The next step would be to move ShellCheck to warning level and this will be 
> quite some work.

Yep!

> But first we need to discuss something.
> 
> If I run ShellCheck in warning level:
> 
> ./script/check-shell-scripts.sh $(pwd) warning
> 
> The warning I see most of the time is:
> 
> warning: In POSIX sh, 'local' is undefined. [SC3043]

This is why I never use local in /bin/sh scripts.  It has never made it
into POSIX.  I suspect the reason is that different shells implemented
different semantics.  For example:

  local foo=$(example --command)

I think local in bash eats the exit code of the subshell.  Other shells
may implement it differently.

I use an "excellent" convention for local variables in /bin/sh scripts,
specially designed to reduce readability.  ;-)  I prefix any local
variable with '_'.  However, it makes no semantic difference, it just
acts as a hint.

> Why do do we use POSIX shell (#/bin/sh) for the majority of our tests (we also 
> have scripts with #!/bin/bash)?

For portability.  I would encourage anyone writing scripts that do not
need bash features to use /bin/sh instead.

In CTDB we have switched our bash scripts (we definitely have some)
to use

  #!/usr/bin/env bash

so they have a chance of working on platforms without /bin/bash.

peace & happiness,
martin