On 10/28/2012 10:50:50 PM, Roy Tam wrote:
Hello,
I noticed that toybox df shows different percentage from GNU df.
GNU df calculates percentage by used/(used+free) while toybox use
(blocks-free)/blocks.
(which one is better by the way?)
According to posix-2008:
<percentage used>
The percentage of the normally available space that is currently
allocated to all
files on the file system. This shall be calculated using the fraction:
<space used>/( <space used>+ <space free>)
expressed as a percentage. This percentage may be greater than 100 if
<space free> is
less than zero. The percentage value shall be expressed as a positive
integer, with
any fractional result causing it to be rounded to the next highest
integer.
The "space used" and "space free" entries are the used/available
displayed in columns 3 and 4. The "any fractional result" implies that
you do something like:
pct=(used*100)/(used+free)
if (pct*(used+free) != (used*100)) pct++;
(Except all with 64 bit math so overflow sucks less.)
toybox$ ../busybox/busybox df
Filesystem 1K-blocks Used Available Use% Mounted on
udev 10240 0 10240 0% /dev
tmpfs 12456 160 12296 1% /run
/dev/disk/by-uuid/4277274d-e9a1-42ff-a247-b75bde522deb
1913244 1151656 664400 63% /
tmpfs 24912 0 24912 0% /run/shm
160/(160+12296.0)
0.012845215157353885
Not doing the pedantic rounding up.
toybox$ df
Filesystem 1K-blocks Used Available Use% Mounted on
rootfs 1913244 1151656 664400 64% /
udev 10240 0 10240 0% /dev
tmpfs 12456 160 12296 2% /run
/dev/disk/by-uuid/4277274d-e9a1-42ff-a247-b75bde522deb
1913244 1151656 664400 64% /
tmpfs 24912 0 24912 0% /run/shm
Doing the pedantic rounding up.
toybox$ ./toybox df
Filesystem 1K-blocks Used Available Use% Mounted on
tmpfs 24912 0 24912 0% /run/shm
/dev/sda1 1913244 1151656 664400 66% /
tmpfs 12456 160 12296 2% /run
udev 10240 0 10240 0% /dev
Showing used as a percentage of 1K-blocks, ignoring "available"
altogether.
Right, I fixed it to match what the standard requires, which seems to
be what upstream is doing.
Thanks for the heads up,
Rob
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