[prog] getting parameters into scripts

[Miriam English]

I normally use positional parameters in scripts, collecting them as $1, 
$2, $3, and so on. This is fine, but I recently wrote a script where it 
would have been really nice to be able to give the parameters in a 
different order under certain circumstances. I filed that away in my 
head until this morning I hit on the idea of doing something like this:

for i in $@; do
     eval "$i"
done

If I give all parameters in the form a=blah or x=nerf then this little 
loop stores the value into a variable called $a or $x in the script. 
This works wonderfully regardless of how many parameters it is fed, 
automatically adapting to how many are given.

My problem is that it trips up if I feed it a parameter with a space in 
it. For example if my script is called testparams and I invoke it this way:

testparams c=turkey a="elephant trunk" b="blob" d='pine cone'

then all variables are stored, but $a contains just "elephant" and $d 
contains just "pine". Weirdly, $2 is "a=elephant trunk" and $4 is 
"d=pine cone", just as you'd expect.

Add this after the above little loop and you'll see what I mean:
echo "named:"
echo $a
echo $b
echo $c
echo $d
echo "positional:"
echo $1
echo $2
echo $3
echo $4

Looking at $@ displays the problem. The quotes have been lost:
c=turkey a=elephant trunk b=blob d=pine cone
so it looks like we have 6 items, even though $# knows there are only 4.

So I tried a different tack:

for i in  $(seq $#); do

and noticed that putting

echo $`echo $i`

inside the loop printed out "$1", "$2", and so on, so I tried (hold onto 
your hat) evaluating that with:

eval `eval "echo $\`echo $i\`"`

but was back to the same old problem again. [sigh]

Anybody know how to get parameters with spaces into those variables?
Or should I just give up on trying to be a mental contortionist? :)

-- 
If you don't have any failures then you're not trying hard enough.
  - Dr. Charles Elachi, director of NASA's Jet Propulsion Laboratory
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Website: http://miriam-english.org
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