Bugs item #851123, was opened at 2003-11-29 07:36
Message generated for change (Comment added) made by greg_ball
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Category: Python Library
Group: Python 2.3
Status: Open
Resolution: None
Priority: 5
Submitted By: Gerald Schlueter (gls62)
Assigned to: Nobody/Anonymous (nobody)
Summary: shutil.copy destroys hard links
Initial Comment:
Hi,
I am using python2.3 on a debian linux (unstable) kernel
Version 2.4.20.
shell:
cd /tmp
cp /etc/passwd a
ln a b
cp a b
*** a and b are the same file ***
python
import shutil
shutil.copy("a", "b")
The file is destroyed and cut down to 0 Bytes!
Thank you,
Gerry (gls62)
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Comment By: Gregory H. Ball (greg_ball)
Date: 2003-12-01 12:03
Message:
Logged In: YES
user_id=11365
The problem is in function shutil.copyfile().
Unlike cp, it does not check whether the two filenames actually
link to the same underlying file. If they do, the act of
opening the dst file for writing destroys the src file.
This is true for symbolic or hard links. cp notices the
link and prints a message.
A fix for this would be to replace the lines
# check for same pathname; all platforms
_src = os.path.normcase(os.path.abspath(src))
_dst = os.path.normcase(os.path.abspath(dst))
if _src == _dst:
return
with
# check for same file
if hasattr(os.path,'samefile'): # Macintosh, Unix.
try:
if os.path.samefile(src,dst):
return
except OSError:
pass
else: # check for same pathname; all other platforms
_src = os.path.normcase(os.path.abspath(src))
_dst = os.path.normcase(os.path.abspath(dst))
if _src == _dst:
return
This should fix the bug under Unix (and Mac, I guess) and
leave other platforms no worse than before (I guess most
other platforms do not have hard or symbolic links anyway?)
I have posted a patch at
http://tane.cfa.harvard.edu/python/shutil.patch
Gerry, could you try it out, then perhaps I can open a patch
item.
I've included some test code. However, it uses
tempfile.mktemp which I see has now been deprecated, so it
will need a fix for that. Also, I'm not sure that it
properly cleans up in the event of a failure. Perhaps this
should be fixed too.
----------------------------------------------------------------------
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