Re: How to get a directory file descriptor?
Steve Holden wrote: Anyway, when I try to use O_RDONLY on Vista I get "Permission denied": According to the library ref, fchdir() is Unix-only, so there probably isn't a use case for getting a file descriptor for a directory on Windows in the first place. -- Greg -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a directory file descriptor?
Steve Holden wrote:
import os
hasattr(os, 'O_DIRECTORY')
True
I'm pretty certain it was present under Windows XP as well.
f = os.open(".", os.O_DIRECTORY)
Traceback (most recent call last):
File "", line 1, in
AttributeError: 'module' object has no attribute 'O_DIRECTORY'
The 3.0 manual lists 4 groups of flags: unix and windows, unix only,
windows only, gnu only (check system-specific manual). O_DIRECTORY is
in the gnu group.
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Re: How to get a directory file descriptor?
Nick Craig-Wood wrote:
> Here is how you do exactly that in python using ctypes
>
> from ctypes import CDLL, c_char_p, c_int, Structure, POINTER
> from ctypes.util import find_library
>
> class c_dir(Structure):
> """Opaque type for directory entries, corresponds to struct DIR"""
> c_dir_p = POINTER(c_dir)
>
> c_lib = CDLL(find_library("c"))
> opendir = c_lib.opendir
> opendir.argtypes = [c_char_p]
> opendir.restype = c_dir_p
> dirfd = c_lib.dirfd
> dirfd.argtypes = [c_dir_p]
> dirfd.restype = c_int
> closedir = c_lib.closedir
> closedir.argtypes = [c_dir_p]
> closedir.restype = c_int
>
> dir_p = opendir(".")
> print "dir_p = %r" % dir_p
> dir_fd = dirfd(dir_p)
> print "dir_fd = %r" % dir_fd
> print "closed (rc %r)" % closedir(dir_p)
>
> Which prints on my linux machine
>
> dir_p =
> dir_fd = 3
> closed (rc 0)
>
> I don't know why os doesn't wrap - opendir, closedir, dirfd, readdir
> etc - I guess because except if you are doing something esoteric, then
> os.list and os.walk do everything you could possibly want.
>
Thank you so much Nick. I'll take a look into the ctypes module.
I guess the reason of Python library not including those wrappers has something
to do with standard compliance. The fchdir(2) manual says "comforming to
POSIX.1-2001" but the opendir(3) manual says "fdopendir() is specified in
POSIX.1-2008."
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Re: How to get a directory file descriptor?
Cong Ma <[EMAIL PROTECTED]> wrote:
> Thanks for your reply. I checked my Python 2.5 install on Linux and there's
> the
> O_DIRECTORY flag. However this is not mentioned anywhere in the Library
> Reference.
>
> There's another question regarding to this flag though: I checked the manual
> of
> the Linux system call open(2), in which there's a paragraph on this flag:
>
> O_DIRECTORY
>If pathname is not a directory, cause the open to fail.
> This
>flag is Linux-specific, and was added in kernel version
> 2.1.126,
>to avoid denial-of-service problems if opendir(3) is called on
> a
>FIFO or tape device, but should not be used outside of
> the
>implementation of opendir(3).
That says avoid to me!
> Note the "should not be used outside of the implementation of opendir(3)"
> part.
> Does that mean using Python's os.open() with the O_DIRECTORY flag is a Bad
> Thing?
IMHO yes.
> In C, I think, calling opendir() followed by dirfd() should be the
> correct way of doing this?
Here is how you do exactly that in python using ctypes
from ctypes import CDLL, c_char_p, c_int, Structure, POINTER
from ctypes.util import find_library
class c_dir(Structure):
"""Opaque type for directory entries, corresponds to struct DIR"""
c_dir_p = POINTER(c_dir)
c_lib = CDLL(find_library("c"))
opendir = c_lib.opendir
opendir.argtypes = [c_char_p]
opendir.restype = c_dir_p
dirfd = c_lib.dirfd
dirfd.argtypes = [c_dir_p]
dirfd.restype = c_int
closedir = c_lib.closedir
closedir.argtypes = [c_dir_p]
closedir.restype = c_int
dir_p = opendir(".")
print "dir_p = %r" % dir_p
dir_fd = dirfd(dir_p)
print "dir_fd = %r" % dir_fd
print "closed (rc %r)" % closedir(dir_p)
Which prints on my linux machine
dir_p =
dir_fd = 3
closed (rc 0)
I don't know why os doesn't wrap - opendir, closedir, dirfd, readdir
etc - I guess because except if you are doing something esoteric, then
os.list and os.walk do everything you could possibly want.
--
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Re: How to get a directory file descriptor?
On Nov 26, 8:56 pm, Cong Ma <[EMAIL PROTECTED]> wrote: > Thanks for your reply. I checked my Python 2.5 install on Linux and there's > the > O_DIRECTORY flag. However this is not mentioned anywhere in the Library > Reference. Yes, I just noticed that myself. > O_DIRECTORY > If pathname is not a directory, cause the open to fail. This > flag is Linux-specific, and was added in kernel version 2.1.126, Well, that certainly explains it's absence :) > Note the "should not be used outside of the implementation of opendir(3)" > part. > Does that mean using Python's os.open() with the O_DIRECTORY flag is a Bad > Thing? I'm sorry, that's outside of my knowledge. But it seemed to work fine when I tried it. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a directory file descriptor?
On Nov 26, 11:07 pm, Steve Holden <[EMAIL PROTECTED]> wrote: > alex23 wrote: > > I'm pretty certain it was present under Windows XP as well. > > Since these two are the exact same version I presume O_DIRECTORY is not > meaningful on Windows. Anyway, when I try to use O_RDONLY on Vista I get > "Permission denied": Sorry, my bad. I got the exact same "Permission denied" response when I first tried this under XP, so I shelled to a linux box and tested there...then promptly forgot all about it. In my defence, it was pretty late at night when I did so :) In fact, I can't even find a reference to O_DIRECTORY in the manual at all... -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a directory file descriptor?
alex23 wrote:
> On Nov 26, 3:26 pm, greg <[EMAIL PROTECTED]> wrote:
>> os.O_DIRECTORY must be fairly new -- it doesn't exist
>> in my 2.5 installation. But os.O_RDONLY seems to work
>> just as well for this purpose.
>
> Which OS are you using?
>
> Python 2.5.2 (r252:60911, Jul 31 2008, 17:28:52)
> [GCC 4.2.3 (Ubuntu 4.2.3-2ubuntu7)] on linux2
> Type "help", "copyright", "credits" or "license" for more information.
import os
hasattr(os, 'O_DIRECTORY')
> True
>
> I'm pretty certain it was present under Windows XP as well.
>
OK, here's a little mystery. This is Vista (spit):
Microsoft Windows [Version 6.0.6001]
Copyright (c) 2006 Microsoft Corporation. All rights reserved.
C:\Users\sholden>python
Python 2.5.2 (r252:60911, Feb 21 2008, 13:11:45) [MSC v.1310 32 bit
(Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> f = os.open(".", os.O_DIRECTORY)
Traceback (most recent call last):
File "", line 1, in
AttributeError: 'module' object has no attribute 'O_DIRECTORY'
>>> hasattr(os, 'O_DIRECTORY')
False
>>>
Since these two are the exact same version I presume O_DIRECTORY is not
meaningful on Windows. Anyway, when I try to use O_RDONLY on Vista I get
"Permission denied":
>>> f = os.open(os.path.abspath("Documents"), os.O_RDONLY)
Traceback (most recent call last):
File "", line 1, in
OSError: [Errno 13] Permission denied: 'C:\\Users\\sholden\\Documents'
regards
Steve
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Holden Web LLC http://www.holdenweb.com/
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Re: How to get a directory file descriptor?
alex23 wrote: > On Nov 26, 3:26 pm, greg <[EMAIL PROTECTED]> wrote: >> os.O_DIRECTORY must be fairly new -- it doesn't exist >> in my 2.5 installation. But os.O_RDONLY seems to work >> just as well for this purpose. > > Which OS are you using? > > Python 2.5.2 (r252:60911, Jul 31 2008, 17:28:52) > [GCC 4.2.3 (Ubuntu 4.2.3-2ubuntu7)] on linux2 > Type "help", "copyright", "credits" or "license" for more information. import os hasattr(os, 'O_DIRECTORY') > True > > I'm pretty certain it was present under Windows XP as well. > > > -- > http://mail.python.org/mailman/listinfo/python-list > Hello, Thanks for your reply. I checked my Python 2.5 install on Linux and there's the O_DIRECTORY flag. However this is not mentioned anywhere in the Library Reference. There's another question regarding to this flag though: I checked the manual of the Linux system call open(2), in which there's a paragraph on this flag: O_DIRECTORY If pathname is not a directory, cause the open to fail. This flag is Linux-specific, and was added in kernel version 2.1.126, to avoid denial-of-service problems if opendir(3) is called on a FIFO or tape device, but should not be used outside of the implementation of opendir(3). Note the "should not be used outside of the implementation of opendir(3)" part. Does that mean using Python's os.open() with the O_DIRECTORY flag is a Bad Thing? In C, I think, calling opendir() followed by dirfd() should be the correct way of doing this? Thanks. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a directory file descriptor?
On Nov 26, 3:26 pm, greg <[EMAIL PROTECTED]> wrote: > os.O_DIRECTORY must be fairly new -- it doesn't exist > in my 2.5 installation. But os.O_RDONLY seems to work > just as well for this purpose. Which OS are you using? Python 2.5.2 (r252:60911, Jul 31 2008, 17:28:52) [GCC 4.2.3 (Ubuntu 4.2.3-2ubuntu7)] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> import os >>> hasattr(os, 'O_DIRECTORY') True I'm pretty certain it was present under Windows XP as well. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a directory file descriptor?
alex23 wrote:
import os
dirfd = os.open("directory-name", os.O_DIRECTORY)
os.fchdir(dirfd)
os.O_DIRECTORY must be fairly new -- it doesn't exist
in my 2.5 installation. But os.O_RDONLY seems to work
just as well for this purpose.
--
Greg
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Re: How to get a directory file descriptor?
On Nov 26, 1:34 pm, Cong Ma <[EMAIL PROTECTED]> wrote:
> So if I can't seem to get directory file descriptors, the only way to use
> os.fchdir() in Python is to embed Python in C code?
This doesn't work for you?
import os
dirfd = os.open("directory-name", os.O_DIRECTORY)
os.fchdir(dirfd)
Are you getting errors? Incorrect behaviour?
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Re: How to get a directory file descriptor?
alex23 wrote: > On Nov 26, 12:31 am, "D'Arcy J.M. Cain" <[EMAIL PROTECTED]> wrote: >> Is this what you want? >> >> ofiles = [open(x) for x in os.listdir(os.getcwd())] > > 'open' returns a "file object", whereas the OP is after "file > descriptors", which are returned by 'os.open'. > > -- > http://mail.python.org/mailman/listinfo/python-list > You got it. So if I can't seem to get directory file descriptors, the only way to use os.fchdir() in Python is to embed Python in C code? -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a directory file descriptor?
On Nov 26, 12:31 am, "D'Arcy J.M. Cain" <[EMAIL PROTECTED]> wrote: > Is this what you want? > > ofiles = [open(x) for x in os.listdir(os.getcwd())] 'open' returns a "file object", whereas the OP is after "file descriptors", which are returned by 'os.open'. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a directory file descriptor?
Cong Ma a écrit :
Dear all,
Can you give me some hint on getting a directory file descriptor in Python?
Besides, what's good about os.fchdir() if I can't get a directory fd in the
first place?
Thanks for your reply.
Regards,
Cong.
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Hello,
I believe you want os.open :
Python 2.5.2 (r252:60911, Sep 29 2008, 21:10:35)
[GCC 4.3.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> d=os.open('mydir',os.O_RDONLY)
>>> d
3
>>> os.fchdir(d)
>>> os.getcwd()
'/home/baptiste/mydir'
>>>
Cheers,
Baptiste
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Re: How to get a directory file descriptor?
On Tue, 25 Nov 2008 16:02:56 +0800 Cong Ma <[EMAIL PROTECTED]> wrote: > >> Can you give me some hint on getting a directory file descriptor in Python? > > for each in os.listdir(os.getcwd()): > > print each > Your code fetches a bunch of strings representing file names in the working > directory, which is fine. But what I want is something like an integer file > descriptor, like the one returned by os.open() for files, or the Linux dirfd() > call, which returns an integer for a pointer to a DIR stream. Is this what you want? ofiles = [open(x) for x in os.listdir(os.getcwd())] -- D'Arcy J.M. Cain <[EMAIL PROTECTED]> | Democracy is three wolves http://www.druid.net/darcy/| and a sheep voting on +1 416 425 1212 (DoD#0082)(eNTP) | what's for dinner. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a directory file descriptor?
On Nov 25, 9:53 pm, alex23 <[EMAIL PROTECTED]> wrote:
> On Nov 25, 5:05 pm, Cong Ma <[EMAIL PROTECTED]> wrote:
>
> > Can you give me some hint on getting a directory file descriptor in Python?
> > Besides, what's good about os.fchdir() if I can't get a directory fd in the
> > first place?
>
> Try: os.open('', os.O_RDONLY)
>
> Check os for a list of the valid flag types.
Sorry, that should probably be os.O_DIRECTORY.
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Re: How to get a directory file descriptor?
On Nov 25, 5:05 pm, Cong Ma <[EMAIL PROTECTED]> wrote:
> Can you give me some hint on getting a directory file descriptor in Python?
> Besides, what's good about os.fchdir() if I can't get a directory fd in the
> first place?
Try: os.open('', os.O_RDONLY)
Check os for a list of the valid flag types.
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Re: How to get a directory file descriptor?
r0g wrote: > Cong Ma wrote: >> r0g wrote: >>> Cong Ma wrote: Dear all, Can you give me some hint on getting a directory file descriptor in Python? Besides, what's good about os.fchdir() if I can't get a directory fd in the first place? Thanks for your reply. Regards, Cong. >>> for each in os.listdir(os.getcwd()): >>> print each >>> >>> Roger. >>> -- >>> http://mail.python.org/mailman/listinfo/python-list >>> >> Roger, >> >> It seemed I didn't make it clearly enough... >> >> Your code fetches a bunch of strings representing file names in the working >> directory, which is fine. But what I want is something like an integer file >> descriptor, like the one returned by os.open() for files, or the Linux >> dirfd() >> call, which returns an integer for a pointer to a DIR stream. >> >> Regards, >> Cong. >> > > Erm, yeah, that's the os.listdir() bit. > > Roger. Actually, just re-reading your last mail, it isn't what you want at all is it?! Sorry! Roger. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a directory file descriptor?
Cong Ma wrote: > r0g wrote: >> Cong Ma wrote: >>> Dear all, >>> >>> Can you give me some hint on getting a directory file descriptor in Python? >>> Besides, what's good about os.fchdir() if I can't get a directory fd in the >>> first place? >>> >>> Thanks for your reply. >>> >>> Regards, >>> Cong. >>> >> for each in os.listdir(os.getcwd()): >> print each >> >> Roger. >> -- >> http://mail.python.org/mailman/listinfo/python-list >> > Roger, > > It seemed I didn't make it clearly enough... > > Your code fetches a bunch of strings representing file names in the working > directory, which is fine. But what I want is something like an integer file > descriptor, like the one returned by os.open() for files, or the Linux dirfd() > call, which returns an integer for a pointer to a DIR stream. > > Regards, > Cong. > Erm, yeah, that's the os.listdir() bit. Roger. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a directory file descriptor?
r0g wrote: > Cong Ma wrote: >> Dear all, >> >> Can you give me some hint on getting a directory file descriptor in Python? >> Besides, what's good about os.fchdir() if I can't get a directory fd in the >> first place? >> >> Thanks for your reply. >> >> Regards, >> Cong. >> > > for each in os.listdir(os.getcwd()): > print each > > Roger. > -- > http://mail.python.org/mailman/listinfo/python-list > Roger, It seemed I didn't make it clearly enough... Your code fetches a bunch of strings representing file names in the working directory, which is fine. But what I want is something like an integer file descriptor, like the one returned by os.open() for files, or the Linux dirfd() call, which returns an integer for a pointer to a DIR stream. Regards, Cong. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a directory file descriptor?
Cong Ma wrote: > Dear all, > > Can you give me some hint on getting a directory file descriptor in Python? > Besides, what's good about os.fchdir() if I can't get a directory fd in the > first place? > > Thanks for your reply. > > Regards, > Cong. > for each in os.listdir(os.getcwd()): print each Roger. -- http://mail.python.org/mailman/listinfo/python-list
