On 10 May, 2013, at 15:54, Antoine Pitrou <solipsis@pitrou.net> wrote:
Le Fri, 10 May 2013 15:46:21 +0200, Christian Heimes <christian@python.org> a écrit :
Am 10.05.2013 14:16, schrieb Antoine Pitrou:
But what if some systems return more than the file type and less than a full stat result? The general problem is POSIX's terrible inertia. I feel that a stat result with some None fields would be an acceptable compromise here.
POSIX only defines the d_ino and d_name members of struct dirent. Linux, BSD and probably some other platforms also happen to provide d_type. The other members of struct dirent (d_reclen, d_namlen) aren't useful in Python space by themselves.
d_type and st_mode aren't compatible in any way. As you know st_mode also contains POSIX permission information. The file type is encoded with a different set of bits, too. Future file types aren't mapped to S_IF* constants for st_mode.
Thank you and Ronald for clarifying. This does make the API design a bit bothersome. We want to expose as much information as possible in a cross-platform way and with a flexible granularity, but doing so might require a gazillion of namedtuple fields (platonically, as much as one field per stat bit).
One field per stat bit is overkill, file permissions are well known enough to keep them as a single item. Most if not all uses of the st_mode field can be covered by adding just "filetype" and "permissions" fields. That would also make it possible to use stat_result in os.scandir() without loosing information (it would have filetype != None and permissions and st_mode == None on systems with d_type).
For d_ino you also need the device number from the directory because the inode is only unique within a device.
But hopefully you've already stat'ed the directory ;)
Why? There's no need to stat the directory when implementing os.walk using os.scandir (for systems that return filetype information in the API used by os.scandir). Anyway, setting st_ino in the result of os.scandir is harmless, even though using st_ino is uncommon. Getting st_dev from the directory isn't good anyway, for example when using rebind mounts to mount a single file into a different directory (which is a convenient way to make a configuration file available in a chroot environment) Ronald
Regards
Antoine.
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