[kai rosenthal] | on UNIX I changed the permission of a file "myfile" with chmod 000 | myfile. Then I got 0 from os.access(myfile, os.R_OK). This is ok. | | Then I checked the same file on WINDOWS (with samba): | I got "True" from os.access(myfile, os.R_OK). I think it is not ok?!
Ummm. This is a touch similar to a parallel thread about os.X_OK on Win32. At the risk of being grilled by better-informed types, the fact is that while the Win32 CRT (used for non-Unicode operations by the Python os module) does expose chmod and access functions, they don't seem guaranteed to do more than overlap more-or-less with the corresponding Unix functions. >From what appears to be the MSDN page for chmod [1]: """ The permission setting controls read and write access to the file. The integer expression pmode contains one or both of the following manifest constants, defined in SYS\STAT.H: _S_IWRITE - Writing permitted _S_IREAD - Reading permitted _S_IREAD | _S_IWRITE - Reading and writing permitted Any other values for pmode are ignored. """ Note that last sentence: I take this to mean that passing zero to mean "can't read or write" is having no effect. The latest Python source source [2] uses the Win32 API SetFileAttributesW [3] where a Unicode filename is passed, but this doesn't seem to allow for a neither-read-nor-write situation either. | In my python script I check the return value of os.access(myfile, | os.R_OK) and when it is "True" I copy the file with | shutil.copy(myfile, newfile). | But on WINDOWS I get the error: IOError: [Errno 13] Permission denied. I suspect you're going to have to put the copy in a try... except block, which is not bad advice in any case. If you check access and then copy, you're at the mercy of a change to the file's permissions (or even existence) between the calls, so you'd have to cope with a potential exception in any case. Better perhaps to do it that way in the first place. This point of view is supported by, among others, GvR in a thread on python-dev. [4] [1] http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vccore9 8/html/_crt__chmod.2c_._wchmod.asp[2] http://svn.python.org/view/python/trunk/Modules/posixmodule.c?rev=51762&; view=auto [3] http://msdn.microsoft.com/library/default.asp?url=/library/en-us/fileio/ fs/setfileattributes.asp [4] http://mail.python.org/pipermail/python-dev/2004-November/049931.html In short, do something like this: <code> try: shutil.copy (myfile, newfile) except IOError: print "Couldn't copy; do useful things or ignore" else: print "Copied ok" </code> TJG ________________________________________________________________________ This e-mail has been scanned for all viruses by Star. The service is powered by MessageLabs. For more information on a proactive anti-virus service working around the clock, around the globe, visit: http://www.star.net.uk ________________________________________________________________________ -- http://mail.python.org/mailman/listinfo/python-list
