[prog] getting parameters into scripts

[Chris Wilson]

Hi Miriam,

On Mon, 29 Mar 2010, Miriam English wrote:

> 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.
[...]
> testparams c=turkey a="elephant trunk" b="blob" d='pine cone'

What about using options with getopt, e.g.

  testparams --c=turkey --a="elephant trunk" 

That would be much, much more standard.

> 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.

Probably because of the eval.

> Looking at $@ displays the problem. The quotes have been lost:
> c=turkey a=elephant trunk b=blob d=pine cone

They are used by the shell to work out the arguments to your script, 
and then removed. I.e. they have a special meaning to the shell, just like 
backticks and $.

> so it looks like we have 6 items, even though $# knows there are only 4.

Only if you try to break them at spaces. You still have $1 == "elephant 
trunk". But if you expand $@, it just concatenates them all together, 
separated by spaces, and of course there are no quotes then.

How about:

  eval `echo $i | sed -e 's/=/="/' -e 's/$/"/'`

which turns:

  a=elephant trunk

into:

  a="elephant trunk"

and then evaluates that?

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

Try getopt.

Cheers, Chris.
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