How can I get the default file permissions in Python?

Question

I am writing a Python script in which I write output to a temporary file and then move that file to its final destination once it is finished and closed. When the script finishes, I want the output file to have the same permissions as if it had been created normally through open(filename,"w"). As it is, the file will have the restrictive set of permissions used by the tempfile module for temp files.

Is there a way for me to figure out what the "default" file permissions for the output file would be if I created it in place, so that I can apply them to the temp file before moving it?

Answer 1

For the record, I had a similar issue, here is the code I have used:

import os
from tempfile import NamedTemporaryFile

def UmaskNamedTemporaryFile(*args, **kargs):
    fdesc = NamedTemporaryFile(*args, **kargs)
    # we need to set umask to get its current value. As noted
    # by Florian Brucker (comment), this is a potential security
    # issue, as it affects all the threads. Considering that it is
    # less a problem to create a file with permissions 000 than 666,
    # we use 666 as the umask temporary value.
    umask = os.umask(0o666)
    os.umask(umask)
    os.chmod(fdesc.name, 0o666 & ~umask)
    return fdesc