New submission from Samson Lee:
I noticed os.fwalk() produced different results as os.walk(). It turned out
that os.fwalk() skips all remaining directories when OSError occurs (e.g. due
to PermissionError).
To reproduce the bug, first create a test directory structure:
$ mkdir 1; touch 1/a
$ mkdir 2; touch 2/b
$ mkdir 3; touch 3/c
$ mkdir 4; touch 4/c
At this stage, everything is okay, both os.fwalk() os.walk() produce the same
results:
>>> import os
>>> for root, dirs, files in os.walk('.'):
... dirs.sort()
... print(root, dirs, files)
. ['1', '2', '3', '4'] []
./1 [] ['a']
./2 [] ['b']
./3 [] ['c']
./4 [] ['d']
>>> for root, dirs, files, fd in os.fwalk('.'):
... dirs.sort()
... print(root, dirs, files)
. ['1', '2', '3', '4'] []
./1 [] ['a']
./2 [] ['b']
./3 [] ['c']
./4 [] ['d']
To introduce an error, force a PermissionError on one of the directories:
$ sudo chown root:root 2
$ sudo chmod 700 2
Now, the os.fwalk() results are different (trust me, os.walk() is still okay):
>>> for root, dirs, files, fd in os.fwalk('.'):
... dirs.sort()
... print(root, dirs, files)
. ['1', '2', '3', '4'] []
./1 [] ['a']
So it seems that os.fwalk skips remaining directories after an error occurs.
The cause of the problem is in this part of os.py:
for name in dirs:
try:
orig_st = stat(name, dir_fd=topfd, follow_symlinks=follow_symlinks)
dirfd = open(name, O_RDONLY, dir_fd=topfd)
except OSError as err:
if onerror is not None:
onerror(err)
break
To fix it, simply replace break with continue. Patch attached.
Cheers
----------
components: Library (Lib)
files: fwalk-silently-skips-dirs-when-error-occurs.patch
keywords: patch
messages: 256377
nosy: Samson Lee
priority: normal
severity: normal
status: open
title: os.fwalk() silently skips remaining directories when error occurs
type: behavior
versions: Python 3.4, Python 3.5
Added file:
http://bugs.python.org/file41304/fwalk-silently-skips-dirs-when-error-occurs.patch
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue25860>
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