Issue 542314: long file name support broken in windows (original) (raw)
Created on 2002-04-11 04:23 by mhammond, last changed 2022-04-10 16:05 by admin. This issue is now closed.
Messages (6)
Author: Mark Hammond (mhammond) * 
Date: 2002-04-11 04:23
From c.l.py, thread ""
Peter D: I'm using windows and trying to call os.path.getmtime () after using os.path.walk... However, I'm choking with "[Errno 38] Filename too long" on paths with len
~260
Adding Martin's reply in a new comment (so it is not at the top of each and every mail I get on this bug :)
Author: Mark Hammond (mhammond) *
Date: 2002-04-11 04:26
Logged In: YES user_id=14198
Martin v. Loewis's reply on c.l.py:
Since you are asking for a work-around: cd into one of the more nested directories when the path gets longer (os.chdir), and use relative paths from then on.
If you want to study how to solve the problem: the relevant code snippet is in Modules/posixmodule.c
/* the library call can blow up if the file name is too long! */ if (pathlen > MAX_PATH) { PyMem_Free(pathfree); errno = ENAMETOOLONG; return posix_error(); }
There might be different ways to approach this:
- challenge the correctness of the comment:
- try to establish why the author of that code thought that the C library could blow up
- analyse whether these arguments are still true with the current compiler version -or-
- prove the argument wrong by analysing the source code of the C library
- then remove the constraint -or-
- use different API to achieve the same effect without suffering from the constraint.
I'm serious about these suggestions: users would appreciate if this gets fixed somehow - apparently, the system allows longer file names, and apparently, the system itself can deal with that quite well. This can be only true if the system either doesn't use its C library, or if the C library does not have this restriction.
Author: Stuart Norton (stunorton)
Date: 2005-03-30 16:54
Logged In: YES user_id=1152606
I came across this suggestion while googling... and I would have expected it to work, but this code:
import os
os.chdir("\\ussvs- \radpubs\wip\zStaging\translation\D10 \previous_test\cumulative\Common\Reference\API\Borland .Eco.Persistence.Configuration\classes\PersistenceMapper DefinitionCollection\Methods") for filename in os.listdir("."): print filename infile = file(filename)
gives me
C:\Documents and Settings\snorton\Desktop\h2build\buildtools>test.py PersistenceMapperDefinitionCollection.AddRange.xml PersistenceMapperDefinitionCollection.Assign.xml PersistenceMapperDefinitionCollection.FindByName.xml PersistenceMapperDefinitionCollection.NameExists.xml PersistenceMapperDefinitionCollection.PersistenceMapperDefi nitionCollection.xml Traceback (most recent call last): File "C:\Documents and Settings\snorton\Desktop\h2build\buildtools\test.py", line 6, in ? infile = file(filename) IOError: [Errno 2] No such file or directory: 'PersistenceMapperDefinitionCollection.Persistence MapperDefinitionCollection.xml'
... funny that the file with the long path comes up in listdir() but isn't found with file()...
Author: Ralf Schmitt (titty)
Date: 2007-03-26 12:36
or if the c library is just insane: from http://msdn2.microsoft.com/en-us/library/aa365247.aspx:
Maximum Path Length
In the Windows API, the maximum length for a path is MAX_PATH, which is defined as 260 characters. A path is structured in the following order: drive letter, colon, backslash, components separated by backslashes, and a null-terminating character, for example, the maximum path on the D drive is D:<256 chars>NUL.
The Unicode versions of several functions permit a maximum path length of approximately 32,000 characters composed of components up to 255 characters in length. To specify that kind of path, use the "\?" prefix.
Note The maximum path of 32,000 characters is approximate, because the "\\?\" prefix can be expanded to a longer string, and the expansion applies to the total length.For example, "\?\D:<path>". To specify such a UNC path, use the "\?\UNC" prefix. For example, "\?\UNC<server><share>". These prefixes are not used as part of the path itself. They indicate that the path should be passed to the system with minimal modification, which means that you cannot use forward slashes to represent path separators, or a period to represent the current directory. Also, you cannot use the "\?" prefix with a relative path. Relative paths are limited to MAX_PATH characters.
When using the API to create a directory, the specified path cannot be so long that you cannot not append an 8.3 file name.
The shell and the file system may have different requirements. It is possible to create a path with the API that the shell UI cannot handle.
the explicit checks for pathnames longer than 260 characters seem to be removed in python 2.5 and one can use the "magic prefix" to stat/create files with pathnames longer than 260 characters.
Author: Brett Cannon (brett.cannon) *
Date: 2007-09-13 23:44
Can someone verify that the length issue has been fixed since Ptyhon 2.5?
Author: Mark Hammond (mhammond) *
Date: 2007-09-15 02:00
I can confirm the code in question was removed and that long filenames are possible in 2.5. Eg:
import os p = "\\?\" + os.getcwdu() for i in range(10): p = os.path.join(p, 'x' * 100) os.mkdir(p) os.stat(p) print len(p)
I don't think Python should try and hide this madness, so I'm marking it as closed.
History
Date
User
Action
Args
2022-04-10 16:05:12
admin
set
github: 36411
2007-09-15 02:00:29
mhammond
set
status: open -> closed
resolution: fixed
messages: +
2007-09-13 23:44:05
brett.cannon
set
nosy: + brett.cannon
messages: +
2002-04-11 04:23:54
mhammond
create