Issue 851123: shutil.copy destroys hard links (original) (raw)

Issue851123

Created on 2003-11-29 12:36 by gls62, last changed 2022-04-11 14:56 by admin. This issue is now closed.

Messages (4)
msg19198 - (view)	Author: Gerald Schlueter (gls62)	Date: 2003-11-29 12:36
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)
msg19199 - (view)	Author: Gregory H. Ball (greg_ball)	Date: 2003-12-01 17:03
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.
msg19200 - (view)	Author: Gerald Schlueter (gls62)	Date: 2003-12-02 15:28
Logged In: YES user_id=920149 Hi Gregory, your patch works fine on my system. greetings, Gerry
msg19201 - (view)	Author: Johannes Gijsbers (jlgijsbers) *	Date: 2004-08-14 13:33
Logged In: YES user_id=469548 Fixed in rev 1.31 of shutil.py using patch at http://python.org/sf/854853.