Parameter Expansion questions

Parameter Expansion questions

[David R. Favor]

In ksh, word splitting occurs auto-magically via setting IFS, thus:

   SAVEIFS="$IFS"
   IFS=:
   splitpath=$PATH
   IFS="$SAVEIFS

results in $splitpath having $PATH contents with ':' characters changed
to blanks.

In zsh, I'm having a challenge deciphering the manual about parameter
expansion options. I've tried the following, without success. All fragments
set $IFS=: before expansion:

   export SH_WORD_SPLIT     // explicit 'set SH_WORD_SPLIT'
   splitpath=$*

and

   splitpath=${=PATH}       // implicit 'set SH_WORD_SPLIT'

and

   splitpath=${buf:s:':':}  // word split s:char:

Can someone let me know what I'm doing wrong in each of these situations?

I did figure out that this works:

   splitpath=${buf:gs/:/ /}

Also,

Also, a pointer to some good examples of parameter expansion would be great.

Thanks.

Re: Parameter Expansion questions

[Zefram]

David R. Favor wrote:
>In zsh, I'm having a challenge deciphering the manual about parameter
>expansion options. I've tried the following, without success. All fragments
>set $IFS=: before expansion:
>
>   export SH_WORD_SPLIT     // explicit 'set SH_WORD_SPLIT'
>   splitpath=$*

zsh doesn't perform field splitting on the RHS of scalar variable
assignments.  Try "echo $*" under equivalent circumstances.

>I did figure out that this works:
>
>   splitpath=${buf:gs/:/ /}

That's doing a substitution, rather than field splitting.  Since the
effect you're asking for is actually a substitution, rather than field
splitting (since you're just joining up the fields again anyway), this
is logically the correct thing to do.

OTOH, I suspect that you *really* want to be using an array parameter.
$path is an array version of $PATH, so you don't even need to do the
splitting manually in that case.

-zefram

Re: Parameter Expansion questions

[Bruce Stephens]

"Zefram" <zefram@tao.co.uk> writes:

> OTOH, I suspect that you *really* want to be using an array
> parameter.  $path is an array version of $PATH, so you don't even
> need to do the splitting manually in that case.

Yes, when I first read it, I came up with

	splitpath="$path"

But that's surely not a particularly useful thing to do.  Well, I
can't think of a use, anyway.  Maybe I'm just not being creative
today.

Re: Parameter Expansion questions

[Bart Schaefer]

On Aug 17,  3:45pm, Zefram wrote:
} Subject: Re: Parameter Expansion questions
}
} zsh doesn't perform field splitting on the RHS of scalar variable
} assignments.

It does when shwordsplit is set, but not with ${=param}.  That seems a
bit counterintuitive.  Of course, you don't really notice unless IFS has
been changed, but ...

-- 
Bart Schaefer                                 Brass Lantern Enterprises
http://www.well.com/user/barts              http://www.brasslantern.com