Re: when options conflict

[Benno Schulenberg]

Charles Levert wrote:
> * On Friday 2005-11-11 at 22:09:17 +0100, Benno Schulenberg wrote:
> > Ideally, what should grep do when options conflict?
> >
> > 1) Abort with an error message.
> > 2) Give a warning and let an arbitrary option take precedence,
> >    depending on how things are implemented.
> > 3) Say nothing and always have the last of the conflicting
> > options determine the outcome.

[Skipping the details for now.]

>          8. ...
>             The use of conflicting
>             mutually-exclusive arguments produces
>             undefined results, 

Okay, so this allows for the current situation, solution 2).

>         11. The order of different options
>             relative to one another should
>             not matter,

This disallows solution 3), which I preferred, but which would be 
complicated anyway.  Well, then I would prefer solution 1), always 
abort if two options cannot both be satisfied: better have no 
output at all instead of output that is different from what one 
thought, not notice it (grep being used in a pipe), and interpret 
the result wrong.

>                         unless the options are 
>             documented as mutually-exclusive
>             and such an option is documented to
>             override any incompatible options
>             preceding it.

This will need to be documented then at least for the -d and -r 
combinations.

>             If an option that 
>             has option-arguments is repeated,
>             the option and option-argument
>             combinations should be interpreted
>             in the order specified on the
>             command line.

This I understand to mean that "-C2 -C5" means "-C5", and "-C5 -C2" 
means "-C2", because if max() was used here, then the order wouldn't 
matter.  GNU grep behaves this way (last one counts), but GNU diff 
simply aborts: "diff: conflicting output style options".

Benno