detecting drives for windows and linux

Florian Diesch diesch at spamfence.net
Tue Mar 28 16:52:03 CEST 2006


aleaxit at yahoo.com (Alex Martelli) wrote:

> Florian Diesch <diesch at spamfence.net> wrote:
>    ...
>> >> are and want to do it anyway?) Linux puts the whole file system 
>> >> (including mounted iPods, ISOs and NTFS drives) in one hierarchy.
>> >
>> > Yes, but you may still want to distinguish (because, for example, hard
>> > linking doesn't work across filesystems, and mv is not atomic then).
>> 
>> Why not use os.stat?
>
> Each os.stat call gives you information about one file (or directory);
> it may be simpler and faster to get the information "in bulk" once and
> for all.

Depends on what you want to do. Offen you need informations like file size,
permissions or owner in any case.


For things like creating hardlinks it may be the best to just try it and
catch the exception.


>> > Running a df command is a good simple way to find out what drives are
>> > mounted to what mountpoints -- the mount command is an alternative, but
>> > its output may be slightly harder to parse than df's.
>> 
>> Executing df may be expensive if it needs to read some slow file systems.
>
> That's what the -n flag is for, if you're worried about that (although
> I believe it may not be available on all systems) -- 

GNU df doesn't have it.
Some of the various version of df at Solaris don't have it too. And they
have at least two different output formats.


> executing mount
> is the alternative (just putting up with some parsing difficulties
> depending, e.g., on what automounters may be doing).

I would prefer mount as ir is cheaper than df

>> Reading /etc/mtab is not difficult and much faster
>
> $ cat /etc/mtab
> cat: /etc/mtab: No such file or directory

Ok, wasn't that clever. On Solaris it's /etc/mntab, I don't have any BSD around

> Oops!  BSD systems don't have /etc/mtab... so, if you choose to get your
> info by reading it, you've just needlessly destroyed your program's
> compatibility with a large portion of the Unix-y universe.  popen a
> mount or df, and information will be easier to extract portably.

On the other hand I know of at least two boxes (no, not mine) where
ordinary users don't have permission to exec mount.





   Florian
-- 
Emacs doesn't crash!  It contains very little C, so there's very
little reason to have it crash. [Pascal Bourguignon in gnu.emacs.help]



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