Need Simple Way To Determine If File Is Executable

[Tim Daneliuk]

Gabriel Genellina wrote:
> On 17 dic, 19:21, "Roger Upole" <rup... at hotmail.com> wrote:
> 
>>>>>   os.stat(selected)[ST_MODE] & (S_IXUSR|S_IXGRP|S_IXOTH
>>>> This will tell you that "x.exe" is executable, even if "x.exe" contains
>>>> nothing but zeros.
>>> Isn't the same with any other recipe, portable or not? Unless the OS
>>> actually tries to load and examine the file contents, which the OS's
>>> I'm aware of, don't do.
>> On windows, you can use win32file.GetBinaryType to check if a file is actually
>> a binary executable.
> 
> A similar function exists on Linux too. But even if a file has the
> right file format, if it does not have the execute bit set, won't run.
> And you could set that bit on a JPG image too - and nothing good would
> happen, I presume. So one must determine first what means "the file is
> executable".
> 

Well... sure, but that isn't the point. Here is the problem I was
trying to solve:

I wrote and maintain the 'twander' cross-platform file browser:

   http://www.tundraware.com/Software/twander/

I was working on a new release and wanted to add file associations
to it.  That is, if the user selected a file and double clicked or
pressed Enter, I wanted the following behavior (in the following
steps, "type" means nothing more than "a file whose name ends with
a particular string"):

1) If an association for that file type exists, run the associated program.

2) If an association for that file type does not exist:

    a) If the file is not "executable", see if there is a "default"
       association defined and run that program if there is.

    b) If the file *is* "executable", run it.


So ... all I really needed to know is whether or not the OS thinks the
file is executable.  Obvious - and this is true on most any system -
you can create the situation where the file appear executable from
the OS's point of view, but it is not actually.  But this is a pathology
that no application should really be expected to cope with...

-- 
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Tim Daneliuk     tundra at tundraware.com
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