[Python-Dev] IO module improvements (original) (raw)

Christian Heimes lists at cheimes.de
Sat Feb 6 00:47:15 CET 2010

Guido van Rossum wrote:

You're right, I didn't see the OP's comma. :-)

I don't think this can be helped though -- I really don't want open() to be slowed down or complicated by an attempt to do path manipulation. If this matters to the app author they should use os.path.abspath() or os.path.realpath() or whatever before calling open().

I had the idea to add a property that returns the file name based on the file descriptor. However there isn't a plain way to lookup the file based on the fd on POSIX OSes. fstat() returns only the inode and device. The combination of inode + device references 0 to n files due to anonymous files and hard links. On POSIX OSes with a /proc file systems it's possible to do a reverse lookup by (ab)using /proc/self/fd/, but that's a hack.

import os f = open("/etc/passwd") fd = f.fileno() os.readlink("/proc/self/fds/%i" % fd) '/etc/passwd'

On Windows it's possible to get the file name from the handle with GetFileInformationByHandleEx().

This doesn't strike me as a feasible options ...

Christian

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