a df option question

> DF(1)                          FSF                          DF(1)

> NAME
>        df - report filesystem disk space usage

> SYNOPSIS
>        df [OPTION]... [FILE]...

> DESCRIPTION
>        This manual page documents the GNU version of df.  df dis­
>        plays the amount of disk space available on the filesystem
>        containing  each  file  name argument.  If no file name is
>        given,  the  space  available  on  all  currently  mounted
>        filesystems is shown.  Disk space is shown in 1K blocks by
>        default, unless the environment  variable  POSIXLY_CORRECT
>        is set, in which case 512-byte blocks are used.

>        If  an argument is the absolute file name of a disk device
>        node containing a mounted filesystem, df shows  the  space
>        available on that filesystem rather than on the filesystem
>        containing the device  node  (which  is  always  the  root
>        filesystem).   This  version  of  df cannot show the space
>        available on unmounted filesystems, because on most  kinds
>        of  systems  doing  so  requires very nonportable intimate
>        knowledge of filesystem structures.

> OPTIONS
>        Show information about the filesystem on which  each  FILE
>        resides, or all filesystems by default.

>        -a, --all
>               include filesystems having 0 blocks

>        --block-size=SIZE use SIZE-byte blocks

>        -h, --human-readable
>               print sizes in human readable format (e.g., 1K 234M
>               2G)

>        -H, --si
>               likewise, but use powers of 1000 not 1024

>        -i, --inodes
>               list inode information instead of block usage

>        -k, --kilobytes
>               like --block-size=1024

>        -l, --local
>               limit listing to local filesystems

>        -m, --megabytes
>               like --block-size=1048576

>        --no-sync
>               do  not  invoke  sync  before  getting  usage  info

> GNU fileutils 4.0p          March 2001                          1

> DF(1)                          FSF                          DF(1)

>               (default)

>        -P, --portability
>               use the POSIX output format

>        --sync invoke sync before getting usage info

>        -t, --type=TYPE
>               limit listing to filesystems of type TYPE

>        -T, --print-type
>               print filesystem type

>        -x, --exclude-type=TYPE
>               limit listing to filesystems not of type TYPE

>        -v     (ignored)

>        --help display this help and exit

>        --version
>               output version information and exit

> AUTHOR
>        Written  by  Torbjorn  Granlund,  David  MacKenzie,  Larry
>        McVoy, and Paul Eggert.

> REPORTING BUGS
>        Report bugs to <bug-fileutils@gnu.org>.

> COPYRIGHT
>        Copyright © 1999 Free Software Foundation, Inc.
>        This is free software; see the source for  copying  condi­
>        tions.  There is NO warranty; not even for MERCHANTABILITY
>        or FITNESS FOR A PARTICULAR PURPOSE.

> SEE ALSO
>        The full documentation for df is maintained as  a  Texinfo
>        manual.    If  the  info  and  df  programs  are  properly
>        installed at your site, the command

>               info df

>        should give you access to the complete manual.

> GNU fileutils 4.0p          March 2001                          2