Re: double quoted expansion question

[Jérémie Roquet <arkanosis@xxxxxxxxx>]

Hi,

2012/9/7 Sebastian Stark <seb-zsh@xxxxxxxxxxx>:
> I am trying to make a unique list of tags that is given in a string with a certain format, e.  g.:
>
>   servers="
>   madeira linux,gpu,users
>   madeira2 linux,gpu,users
>   smtp linux,mail,smtp
>   isar linux,users
>   easygwa linux,web,external
>   "
>
> The format is: server name, space, tag, comma, tag, comma, tag ...
>
> What I want from the above list is this:
>
>   external gpu linux mail smtp users web
>
> and I get it with:
>
>   print  ${(s:,:uo)${(j:,:)${${(f)servers}//* /}}}
>
> However, if I do this:
>
>   print "${(s:,:uo)${(j:,:)${${(f)servers}//* /}}}"
>
> I get:
>
>   external linux web
>
> This also happens when I use the variable expansion expression in a here document, which, I suppose, is undergoing the same treatment as double quoted strings.
>
> What I would like to understand here is why the output changes the way it does when I add double quotes around my expression. I would expect the same output as without. If anybody could shed some light please, I guess it's just something obvious I cannot see.

I'm not 100 % sure, but I suppose the quotes prevents the shell from
splitting your string on $IFS, so you only have *one* string, and the
“//* /" expression suppresses everything before the last space,
leaving only the tags of the last line.

Best regards,

-- 
Jérémie