bug#7042: df --help does not show `-m' option (original) (raw)

[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

From: Pádraig Brady
Subject: bug#7042: df --help does not show `-m' option
Date: Fri, 17 Sep 2010 09:56:57 +0100
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.8) Gecko/20100227 Thunderbird/3.0.3

On 16/09/10 23:34, Paul Eggert wrote:

On 09/16/10 11:21, Eric Blake wrote: > document -m, with --block-size=M as the long-option spelling > add -g, with --block-size=G as the long-option spelling

This doesn't sound like a good idea. Multi-terabyte disks are already here, and "df -t" is already taken. Also, "df -g" already means something different in Solaris.

Is it really that hard to type "df -Bg"?

Yes I agree the current unit selection options are fine.

If we're going to make incompatible changes, I suggest that we solve the problem once and for all, by having "df" choose the default blocksize dynamically, based on the size of the output line describing the smallest disk. For example, where "df" currently outputs this:

Filesystem 1K-blocks Used Available Use% Mounted on /dev/sda1 11620338002 1437021 11618900981 1% /r/opt /dev/sda2 20971520 1335871 19635650 7% /home/eggert

"df" would notice that the smallest file system is between 1GB and 1TB, so it would default to 1 GB blocks, as follows:

Filesystem 1GB-blocks Used Available Use% Mounted on /dev/sda1 11900GB 2GB 11898GB 1% /r/opt /dev/sda2 22GB 2GB 21GB 7% /home/eggert

This is much more useful as an output format, because one can visually see which file systems are larger by seeing how many digits are there. Contrast this to the output of df --si:

Filesystem Size Used Avail Use% Mounted on /dev/sda1 12T 1.5G 12T 1% /r/opt /dev/sda2 22G 1.4G 21G 7% /home/eggert

which is harder to visually parse that way.

That would break lots of scripts I'd say (they should use -P, but many don't). In any case I don't think there is enough benefit in such a format change given the common wide range of device sizes attached to systems. Personally I find the df -h format easiest to read.

While we're at it, we should fix "df" so that its columns line up better; that would be another incompatible change, but it'd be worth it on hosts where the file system names are long.

We definitely should do this to support languages with side column headings, and df -B\'1 I've an unfinished local branch to do this with mbsalign()

cheers, Pádraig.