Re: [Help-bash] Assigning builtins behavior

[Quentin L'Hours]

On 2018-01-07 06:31 PM, Andy Chu wrote:
> FWIW, here is another case where the shell parser has knowledge of the 
> '=' character in assignments.  It's not just an opaque string to a 
> builtin (e.g. as in 'env').
>
> $ echo x-~andy
> x-~andy
>
> $ echo x=~andy
> x=/home/andy
>
> So although no assignments are made, merely changing the - character to 
> = causes tilde expansion to be triggered.
>
> Dash has the opposite behavior, which IMO is very annoying and inconsistent:
>
> x=~andy  # YES tilde expansion in dash
> readonly x=~andy  # NO tilde expansion in dash

This is pretty interesting, I totally understand that you would want the 
same behavior when adding a simple command on the left, I mean this 
would be pretty confusing to have different outputs like dash does.

However I find it also really confusing that = has such power, meaning 
if you always think your command args should split when they contain an 
IFS character before field splitting then the result is quite 
unexpected. I guess that's why I find the result of dash more logic.

But bash way of treating the = sign seems indeed safer and honestly the 
a=$(echo 1 b=2) splitting is pretty unlikely to be a behavior you'd want 
in a script.

--
Quentin