Re: [Help-bash] pattern replacement experiment

[Ken Irving]

On Wed, Mar 21, 2012 at 12:55:05PM -0600, Bill Gradwohl wrote:
> answer='012345'
> modifier='?/.'
> echo $answer ${answer//?/.} ${answer//${modifier}}
> 
> address@hidden ycc# ./tst
> 012345 ...... 012345
> 
> I expected either for it to work or give me 'bad substitution'.
> 
> I didn't expect what I got.
> 
> Is it because ${modifier} is considered the pattern only , and not the
> pattern plus the string?

It seems odd to try to put part of the substitution operator in a
variable.  I guess you're expecting $modifier to be expanded in place
like a preprocessor macro?  Eval would probably do what you want I 
suppose, but it works with variables holding the parameters separately:

    $ answer=012345
    $ pat=?
    $ sub=y
    $ echo $answer ${answer//?/.} ${answer//$pat/$sub} 
    012345 ...... yyyyyy

Ken