[ python-Bugs-1438480 ] shutil.move raises OSError when copystat fails

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Bugs item #1438480, was opened at 2006-02-25 06:26
Message generated for change (Comment added) made by thomaswaldmann
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Category: Python Library
Group: Python 2.4
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Joe Wreschnig (piman)
Assigned to: Nobody/Anonymous (nobody)
Summary: shutil.move raises OSError when copystat fails

Initial Comment:
If you are on a Linux system, and shutil.move a file
from anywhere onto a partition where you have write
permission but are not the owner, os.utime will fail
with an EPERM OSError. This can (and did) happen moving
a file on a vfat partition mounted with umask=0000, so
every user had read/write/execute but all files were
owned by root.

This happens in shutil.copystat, so shutil.move doesn't
remove the old file. The resulting error code (OSError,
EPERM) is not distinguishable from several other
permission errors that can happen during shutil.move,
even though a failure to set a utime is not fatal for
most move operations (mv(1) succeeds, for example).

I would suggest either ignoring an EPERM from copystat,
or catching it in shutil.copy2 and raising a more
specific exception so that it can be easily
distinguished from genuine failure due to permissions.

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Comment By: Thomas Waldmann (thomaswaldmann)
Date: 2007-03-24 19:51

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See also
http://sourceforge.net/tracker/index.php?func=detail&aid=1666318&group_id=5470&atid=105470
for a similar problem with copystat.




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Comment By: Joe Wreschnig (piman)
Date: 2006-02-26 06:08

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The attached patch causes shutil.copy and shutil.copy2 (and
so copytree, and move) to ignore EACCES and EPERM from
copymode and copystat respectively. Other errors are
reraised with the original traceback. Any error copying the
file, rather than the metadata, is still considered fatal.
User calls to copymode and copystat still fail as before.

Justification: On Linux, utime(2) says the distinction
between EACCES and EPERM is blurry and "Linux is not careful
to distinguish between the EACCES and EPERM" so the patch
ignores both. In my opinion, anyone wanting to deal with
low-level details like mtimes and modes is probably not
using shutil, so ignoring is better than a new exception
(which would just result in complicated new code, and
surprise old code). It's also easy for a caller to check if
the mode/utimes were copied, if it's important to them.

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