[Pythonmac-SIG] detecting aliases

[Lee Cullens]

Thanks for the reply Bob.  I've been digging around in the Python  
Documentation Macintosh and more specifically Carbon.File.
(All seems to be a bit of a secret society :~) with scant docs that  
are not up to date and no content in __doc__s so it's a little hard  
going)

What you noted doesn't seem to work verbatim for me, but noting the  
following from the Python site googling:
ResolveAliasFile(file)    Resolve an alias file. Returns a 3-tuple  
(fsspec, isfolder, aliased) where fsspec is the resulting FSSpec  
object,  isfolder is true if fsspec points to a folder and aliased is  
true if the file was an alias in the first place (otherwise the  
FSSpec object for the file itself is returned).


and following your lead I got the following where ppath is an Aqua  
alias to a folder so I need to check for an Aqua alias to a file:
 >>> FSResolveAliasFile(ppath, 1)
(<Carbon.File.FSRef object at 0xe0a70>, 1, 1)
 >>> FSResolveAliasFile(ppath, 1)[0].as_pathname()
'/Library/Documentation'

with the FSRef though I get the following
 >>> def is_alias(ppath):
...      return FSRef(ppath)[0]
...
 >>> ppath = '/Users/Chinook/Documents/Personal/Sys Documentation  
alias 1'
 >>> is_alias(ppath)
Traceback (most recent call last):
   File "/Applications/WingIDE-Professional-2.0.3/WingIDE.app/ 
Contents/MacOS/src/debug/server/_sandbox.py", line 1, in ?
     # Used internally for debug sandbox under external interpreter
   File "/Applications/WingIDE-Professional-2.0.3/WingIDE.app/ 
Contents/MacOS/src/debug/server/_sandbox.py", line 2, in is_alias
     if __name__ == '__main__':
TypeError: unsubscriptable object

Or from the Terminal:
Python 2.4.1 (#2, Mar 31 2005, 00:05:10)
[GCC 3.3 20030304 (Apple Computer, Inc. build 1666)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
 >>> import os
 >>> from Carbon.File import FSResolveAliasFile, FSRef
 >>> FSRef('/Users/Chinook/Documents/Personal/Sys Documentation alias  
1')
<Carbon.File.FSRef object at 0x16cd8>
 >>> def is_alias(ppath):
...   return FSRef(ppath)[0]
...
 >>> ppath = '/Users/Chinook/Documents/Personal/Sys Documentation  
alias 1'
 >>> is_alias(ppath)
Traceback (most recent call last):
   File "<stdin>", line 1, in ?
   File "<stdin>", line 2, in is_alias
TypeError: unsubscriptable object
 >>>


Guess I'll have to do some more googling, but it (tentatively) looks  
like I'm getting back a file ref object as if .data is a default and  
I have to look at what other methods are available.

Thanks again,
Lee C



On Jun 5, 2005, at 11:02 PM, Bob Ippolito wrote:

>
> On Jun 5, 2005, at 7:09 PM, Lee Cullens wrote:
>
>
>> One of my little utilities needs to know when it encounters links/
>> aliases.
>>
>> I can of course detect a Unix symbolic link with os.path.islink
>> ('path') and determine what it points to with os.readlink('path'),
>> but an Aqua alias only triggers os.isfile and it has a size of zero.
>> The size is not a reliable indicator though and I was wondering how
>> (in Python) to detect such and determine what it points to.
>>
>> Is this one of those OS unique things where I need to get into the
>> dev tools to resolve? I've been putting such off till I get into
>> ObjC, since Bob said I would understand the interfaces better then.
>>
>
> Aliases have nothing to do with Objective-C, they're only dealt  
> with from Carbon.
>
> import os
> from Carbon.File import FSResolveAliasFile, FSRef
>
> def resolve_alias(path):
>     # resolve an alias, if not an alias then it will just return the
>     # given path.
>     return FSResolveAliasFile(path, True)[0].as_pathname()
>
> def is_alias(path):
>     # return 1 if an alias, 0 otherwise
>     return FSRef(path)[0]
>
> -bob
>
>

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