Quoted form of the POSIX path & drag n drop

Question

Hi. I have the following situation: A part of a script-application that copies files over the network checks if there is actually enough disc space left on the target volume using the df and du commands.
This is how I do it:
on open (dragged_items)
my handleFiles(draggeditems)
end open
on handleFiles(theseitems)
set the item_sizecheck to the quoted form of the POSIX path of these_items
do shell script ("du -sk " & item_sizecheck & " | awk '{print $1}'")
set x to the result
set destination to "/Volumes/basti"
do shell script ("df -k " & destination & " | xargs echo | awk '{print $11}'")
set y to the result
if x ≤ y then
display dialog "space there"
end if
if x ≥ y then
display dialog "no space"
end if
end handle_Files
Of course in the orininal script instead of displaying a dialog that there is enough space the script will simply copy the files.
The problem now is that I can't get the "quoted form of the POSIX path" for many items at the same time (let's say I want to copy 3 things simultaniously).
So I think I have to cycle through the items (set this_item to item i of these_items),but then I have a problem:
I think checking the filesize/discsize is easiest done by the simple equasion (x larger than y),but if i do this for many objekts i have to use a unknown number of variables.
example:
x1 would be the first of the 3 items I draged onto my application,x2 is the second and x3 the third (...)
Then I would have to add up the filesizes of all these items using du,and then compare it to the available disc space ((x1x2x3) greater than y).
How do I do this?

Answer 1

>For what do I need the Applescript Text delimiters,what do they do?
Text Item Delimiters are used by AppleScript anytime to convert a list to/from a text object.
Imagine you have a list myList containing the strings {"A", "B", "C", "D"}
If you ask AppleScript to:
<pre class=command>set myString to myList as text</pre>
You get:
<pre class=command>ABCD</pre>
However, if you set the TIDs to a space first, AppleScript inserts that between each item in the list:
<pre class=command>set my text item delimiters to space
set myString to myList as text</pre>
Now you get:
<pre class=command>A B C D</pre>
You can use any text string you like - it'll be inserted between each item in the list as it's coerced (or, if you're going from a string to a list, the list items will be delimited by the TIDs).
It's relevant in this example because you're trying to pass multiple file paths to a shell command. The shell requires each argument to be delimited by a space. If you didn't set the TIDs you'd end up with a shell command that looks something like:
<pre class=command>du sk /path/to/file1/path/to/file2/path/to/file3</pre>
which the shell will interpret as a single path. By using a space for your TID you get:
<pre class=command>du sk /path/to/file1 /path/to/file2 /path/to/file3</pre>
which works (assuming the paths are valid, of course).
The one gotcha with setting TIDs is that they're persistent. If you change them at one point in your script, they stay until they're changed again. This often causes confusion when debugging scripts because the TIDs are set somewhere else in the script that you're not currently focussing on. So you should always get in the habit of storing the current TID, making your coercion, then resetting the TIDs to the previous value afterwards - that way you always know you're safe:
<pre class=command>set oldTIDs to my text item delimiters -- save the current TIDs
set my text item delimiters to space -- set the TIDs to what you want
set myString to myList as text -- make your coercion
set my text item delimiters to oldTIDS -- then restore the previous value</pre>