[ python-Bugs-1336582 ] fileinput device or resource busy error

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Bugs item #1336582, was opened at 2005-10-24 17:03
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Category: Unicode
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: A. Murat EREN (meren)
Assigned to: M.-A. Lemburg (lemburg)
Summary: fileinput device or resource busy error

Initial Comment:
Fileinput module can't work with the unicode path names
properly.

Here is the reproduction of the error:

---------------8<---------------8<---------------8<---------------8<-------
meren at pardus /home/meren $ touch myfile
meren at pardus /home/meren $ python
>>> fn = u'/home/meren/myfile'
>>> type(fn)
<type 'unicode'>
>>> import fileinput
>>> for line in fileinput.input(fn, inplace = 1):
...     print line
...
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "/usr/lib/python2.3/fileinput.py", line 231, in next
    line = self.readline()
  File "/usr/lib/python2.3/fileinput.py", line 300, in
readline
    os.rename(self._filename, self._backupfilename)
OSError: [Errno 16] Device or resource busy
>>> 
--------------->8--------------->8--------------->8--------------->8-------

This is happening, because the value of the
self._filename variable is just the first character of
the fn: '/'.

The __init__ method of the FileInput class
(/usr/lib/python2.3/fileinput.py) is the responsible
one about this malfunction. In the __init__ function
it's checking the type of the 'files' variable (in this
case it is fn) for an iteration hack:

---------------8<---------------8<---------------8<---------------8<-------
(...)
    def __init__(self, files=None, inplace=0,
backup="", bufsize=0):
        if type(files) == type(''):
            files = (files,)
(...)
--------------->8--------------->8--------------->8--------------->8-------

When the type of the 'files' variable is unicode, the
value of the 'files' variable is incohorently becoming
into this:

files = [u'/', u'h', u'o', u'm', u'e', u'/', u'm',
u'e', u'r', u'e' ....

consequently, python is trying to execute
os.rename('/', '/.bak') instead of
os.rename('/home/meren/myfile',
'/home/meren/myfile.bak'). After this function call os
module decides to throw an error, normally..

[1],
        (...)
        if isinstance(files, basestring):
            files = (files,)
        (...)

[2]
        (...)
        if type(files) == type(''):
            files = (files,)
        (...)

Checking the type of the variable in the __init__
function of the class like [1] is solving the problem
(now we are doing it like [2]).. Also, no backward
compatibility problem appearing with this replacement.

Here is a small patch to show replacement properly:


---------------8<---------------8<---------------8<---------------8<-------
--- fileinput.orig.py   2005-10-24 19:55:53.019413368 +0300
+++ fileinput.py        2005-10-24 19:56:19.590373968 +0300
@@ -184,7 +184,7 @@
     """

     def __init__(self, files=None, inplace=0,
backup="", bufsize=0):
-        if type(files) == type(''):
+        if isinstance(files, basestring):
             files = (files,)
         else:
             if files is None:
--------------->8--------------->8--------------->8--------------->8-------


and here is the result of the same operation after this
patch:


---------------8<---------------8<---------------8<---------------8<-------
(...)
    os.rename(self._filename, self._backupfilename)
OSError: [Errno 16] Device or resource busy
>>> reload(fileinput)
<module 'fileinput' from '/usr/lib/python2.3/fileinput.py'>
>>> for line in fileinput.input(fn, inplace = 1):
...     print line
...
>>>
--------------->8--------------->8--------------->8--------------->8-------


Sorry for the long explanation,
Thanks in advice..
Ciao.

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