How does 'Create Folder' give its result?

[Richard Gaskin]

Graham Samuel wrote:

> I have a path in a variable say myPath, and I execute
> 
> create folder myPath
> 
> sometimes the folder can't be created (if the directory is protected  
> etc) and if I execute the above in the message box in these  
> circumstances, I see the text
> 
>    can't create that directory
> 
> But if I do this by script, this text doesn't seem to be in 'the  
> result' or in 'it' (which appears to contain 'OK' even if the create  
> hasn't worked), so where is this text - ? The 2.7.0 docs (dictionary  
> and PDF) are silent on the matter. As 'create' is not a function, I  
> don't see any other way for it to return a value.
> 
> Clearly I can produce a workaround by checking if the folder exists  
> immediately after trying to create it, but how does 'create' show its  
> result"?

That's the easy part, "the result":

    create folder myPath
    if the result is not empty then
      answer the result
      exit to top
    end if

The hard part is determining exactly what went wrong.  When a file or 
folder creation error happens, in most cases all the result says is 
"can't create file" or "can't create folder" with no further 
explanation.  How do you advise your users?

The trick is the sysError function, which queries the OS to obtain the 
specific error code associated with the failure.  So you could do 
something like:

    create folder myPath
    if the result is not empty then
      answer the result &" (" sysError() &")"
      exit to top
    end if

That'll give you a specific error code:

    can't create directory (43)

That at least allows your users to give you an error code number when 
they call your tech support line, but I'm a big fan of reducing those 
calls altogether when I can, and that means finding out the meaning of 
all the OS error codes for each supported platform, and building in a 
lookup table to present more meaningful info to the user.

A while back I posted a request for pointers to those codes:
<http://mail.runrev.com/pipermail/use-revolution/2006-February/076890.html>

I've turned up some, but I have too many for Win32 and very few for OS 
X.  While I winnow the Win list down to a manageable subset of common 
culprits, if someone out there has a link to OS X error codes I'd 
certainly appreciate it, and show that appreciation with a modest 
library to make those lookups.

--
  Richard Gaskin
  Managing Editor, revJournal
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