df enhancment for removable media

[Juergen Weigert]

Hi coreutils people!

On a recent SUSE Linux df became unreliable for e.g. USB-drives.
This is because hald automatically mounts and unmounts such drives
as they are accessed.

Usually I get something like:

$ df /media/USB_DISK
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/sda1                    0         0         0   -  /media/USB_DISK

only if the USB_DISK is being accessed, I get the expected output.

$ ls /media/USB_DISK > /dev/null; df /media/USB_DISK
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/sda1               252522    238718     13804  95% /media/USB_DISK

A simple enhancement for df is to actively access the USB_DISK while running
statfs(). I've added an opendir() call in the attached patch. This can be
suppressed with a new commandline option -n. 

Please keep me in CC, I am not subscribed.

thanks,
        Jw.

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coreutils-cvs-df-media-mount.diff
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