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Re: Question about variables and for loop


From: Alexander Elgert
Subject: Re: Question about variables and for loop
Date: Sun, 19 Mar 2006 20:08:32 +0100
User-agent: Mutt/1.4.1i

Paul Jarc schrieb am 18.03.2006 um 20:44:17 (-0500):
> Bob <address@hidden> wrote:
> >     XXX='a "b c" d'
> >     for x in $XXX ; do
> >             echo $x
> >     done
> 
> XXX='a "b c" d'
> eval "set $XXX"
> for x in "$@" ; do
>       echo $x
> done
> 
> If the first element in XXX might start with "-", then it takes a
> little more work to ensure it isn't misinterpreted as an option to
> "set":
> eval "set x $XXX"
> shift
> 

I would use arrays to complete this task, because it is quite hard to
escape a string for the eval-set construct. There is no need to, look at
this (simple?) solution:

        x=("-" 0tt a x) # creating array
        for t in "address@hidden"; do echo "$t"; done
        #             ^ iterating over all array elements

Because this command does not use eval it is faster and safer;
f.e. you can't add commands in the XXX string, like this:
        XXX='a b ; ls -la' # ls -la is executed by eval.

To get rid of you "first element is '-' problem" you can switch off
the option parsing with a single dash or a double dash:
        set -- -xxx
        set - -xxx
In both cases "$1" would be "-xxx".

Alexander




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