Re: Bash substrings: wish for support for negative length (read till n from end)

[Richard Neill]

Jan Schampera wrote:
> Richard Neill wrote:
> 
>> $ echo ${stringZ:2: -1}              #Wish: start at 2, read till
>> ERROR                                #1 before the end. i.e.
>>                              # cde
>>
>> $ echo ${stringZ: -3: -1}    #Wish: start 3 back, read till
>> ERROR                                #1 before the end. i.e.
> 
> Use (-1), i.e.
> 
> $ echo ${stringZ:2:(-1)}
> 
> See also
> http://bash-hackers.org/wiki/doku.php/syntax/pe#substring_expansion (at
> bottom of the section).
> 

Dear Jan,

Thanks for your comment. I now understand why
    echo ${stringZ:-1}   is invalid, and it has to be
    echo ${stringZ:(-1)}   or   echo ${stringZ: -1}

BUT, the example that you gave doesn't actually work; it returns with
an error:
     -bash: (-1): substring expression < 0

My point is that, though the first parameter (offset) may be negative,
the second parameter (length) can only be positive. This is what would
be useful to change.

Thanks,

Richard