Re: It is possible to remove the readonly attribute from {BASH, SHELL}OPTS

[Chet Ramey]

On 1/24/24 7:06 PM, Emanuele Torre wrote:
> I recently discovered that it is possible to set attributes on readonly
> variables

You've been able to set attributes on readonly variables forever. Even the
historical Bourne shell allowed you to export readonly variables.

>    $ declare -p PPID
>    declare -ir PPID="759437"
>    $ declare -l PPID
>    $ declare -p PPID
>    declare -irl PPID="759437"
>
> I noticed SHELLOPTS and BASHOPTS among the default readonly variables
> set by bash.
> They are modified by bash whenever you set a set option or shopt.
>
> I tried setting the -i attribute on them, and got this result:

Well, is this a "my arm hurts when I do this" problem, or should bash
restrict the types of attributes that can be set on readonly variables?

> The arithmetic syntax error caused by trying to assign the new list of
> options to SHELLOPTS prevents bash from changing its value, and
> re-adding the readonly attribute to SHELLOPTS.

That's clearly a problem that needs to be fixed.

> Then SHELLOPTS can be modified, and unset freely. :-)
>
> The same is possible with BASHOPTS.

Sure, it's a problem that you can do it, but it's not really harmful.

Chet

--
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    chet@case.edu    http://tiswww.cwru.edu/~chet/