Re: getopts doesn't properly update OPTIND when called from function

[Harald van Dijk <harald@gigawatt.nl>]

On 01/06/2015 08:29, Herbert Xu wrote:
> On Fri, May 29, 2015 at 07:50:09AM +0200, Harald van Dijk wrote:
>>
>> But the test script in this thread does invoke getopts with
>> parameters that are the same in all invocations, and without
>> modifying OPTIND. I don't see anything else in the normative
>> sections that would make the result undefined or unspecified either.
>> I do think the script is valid, and the results in dash should match
>> those of other shells.
>
> The bash behaviour makes it impossible to call shell functions
> that invoke getopts while in the middle of an getopts loop.
 >
> IMHO the dash behaviour makes a lot more sense since a function
> always brings with it a new set of parameters.  That plus the
> fact that this behaviour has been there since day one makes me
> reluctant to change it since the POSIX wording is not all that
> clear.

True. Given that almost no shell supports that anyway, there can't be 
too many scripts that rely on it, but I did warn about the risk of 
breaking another type of existing scripts as well, I agree that's a real 
concern.

One thing that doesn't really make sense, though: if the getopts 
internal state is local to a function, then OPTIND and OPTARG really 
should be too. Because they aren't, nested getopts loops already don't 
really work in a useful way in dash, because the inner loop overwrites 
the OPTIND and OPTARG variables. While OPTARG will typically be checked 
right at the start of the loop, before any inner loop executes, OPTIND 
is typically used at the end of the loop, in combination with the shift 
command. The current behaviour makes the OPTIND value in that case 
unreliable.

So either way, I think something should change. But if you prefer to get 
clarification first about the intended meaning of the POSIX wording, 
that certainly seems reasonable to me.

> Cheers,