Re: Why is -- in the output of declare -p x?

[alex xmb ratchev]

On Wed, Jan 25, 2023, 6:06 PM Peng Yu <pengyu.ut@gmail.com> wrote:

> help says `-p   display the attributes and value of each NAME`. I'd
> assume at least one purpose is for human to read. If so, then it is
> better to remove the unnecessary -- whenever possible.
>
> After all, the program which uses -p has control to what variable
> names should be used. It can choose variable names such that -- is
> never needed, in such case, those programs never need to test whether
> there is -- or not.
>
> On 1/25/23, Koichi Murase <myoga.murase@gmail.com> wrote:
> > 2023年1月25日(水) 7:22 Peng Yu <pengyu.ut@gmail.com>:
> >> I see -- in the output of declare -p x. Why is it necessary to keep it
> >> there? Is it better to remove it for brevity? Thanks.
> >
> > There can be different kinds of uses for the output of `declare -p'.
> > An obvious one is for humans to check the state of the variable, for
> > which brevity could be useful. Another one is to serialize the state
> > of the variable into a string for later `eval's, for which brevity is
> > mostly irrelevant (except that it might reduce the size a bit). Even
> > another one is for external programs or shell scripts to read the
> > state of the variable, for which consistency wins over brevity.
> >
> > I don't know what is the original intent of this behavior, but it
> > would be useful to always have the variable assignment as the third
> > word when one wants to manipulate the output of `declare -p' in a
> > program. Otherwise, the program needs to make a test against the value
> > of the second word to judge which word it should pick.
> >
>

1) help says 'attributes' , in your case --
1.5) declare -a a=( ) ; declare -p a

2) -- is a big common unix style that says 'no more --arguments parsing'
2.5) cmd --arg -- --noarg

xmb

>
> --
> Regards,
> Peng
>
>