Re: Can I test if a parameter expansion has worked

[zzapper <zsh@xxxxxxxxxxxxxx>]

On 14/09/2022 11:03, zzapper wrote:
> Hi
>
> Q1) Can I test if a parameter expansion has 'fired'?
>
> other than by testing if input == output
Bit embarrassed I didn't provide an example :(

so here it is

# adding a prefix '_s' to an image name

f=stuff.jpg;

print ${f/%(#m).[pjg][npi]e#[gf]/_s$MATCH}

stuff_s.jpg  # good this is what i want

# now pass 'bad' input

f=stuff.txt;

print ${f/%(#m).[pjg][npi]e#[gf]/_s$MATCH}
stuff.txt  #  expansion has obviously left the input unchanged but can I 
test for that???

I suppose I should be testing the filename before passing it to the 
expansion

if [[ $f =~ '.jpg|gif|png|jpeg' ]] ;then echo 'ok' ;else echo 'nok' ;fi