[kwlug-disc] fish vs bash: a progress bar from YSAP and some timing measurements

[William Park]

On 2025-08-24 00:33, Ron wrote:
> I've never used the ${!i} syntax in bash, although I've seen it.
> 
> What does that do?

Indirection.  Eg.
     set -- aa bb cc dd ee
     i=2
     echo $i ${!i}


> ${!prefix*}
> ${!prefix@}
>    Names matching prefix.  Expands to the names  of  variables  whose
>    names  begin  with prefix, separated by the first character of the
>    IFS special variable.  When @ is used and  the  expansion  appears
>    within  double  quotes,  each  variable name expands to a separate
>    word.
> 
> I actually don't understand what this is telling me.

It just returns list of variables whose name start with string 'prefix'. 
  Useful if you created abc001, abc002, abc003, ..., and want to go 
through them.  Eg.
     a1=11 a2=22 a3=33 abc=44
     echo ${!a*}