cut / grep and df -h

Question

How can I grep or cut the "173G" under "Verf"?

I need this for Unix scripting in school.

jonas@jonaspc:~/$ df -h /dev/sda2
Dateisystem    Größe Benutzt Verf. Verw% Eingehängt auf
/dev/sda2       293G    121G  173G   42% /media/Windows

Answer 1

The most comfortable solution for such task is awk:

df -h /dev/sda2 | awk 'NR==2{print$4}'

Or if more partitions are listed, you can pick the right line by the mount point:

df -h | awk '$1=="/dev/sda2"{print$4}'

Is also simple with sed, but less nice if you need to debug it a few mounts later :

df -h /dev/sda2 | sed -rn '2s/^((\S+)\s+){4}.*/\2/p'

df -h | sed -rn '/^\/dev\/sda2/s/^((\S+)\s+){4}.*/\2/p'

That supposes GNU sed. POSIX compatible syntax includes many escaping:

df -h /dev/sda2 | sed -n '2s/^\(\(\S\+\)\s\+\)\{4\}.*/\2/p'

df -h | sed -n '/^\/dev\/sda2/s/^\(\(\S\+\)\s\+\)\{4\}.*/\2/p'

Answer 2

If you must use grep and cut, you can do the following:

df -h /dev/sda2 | grep sda | cut -d" " -f14

But this is pretty ugly, since you have to count the spaces (-f14) and the reason @manatwork used awk. You could use tr or other tools to make it nicer and be able to specify the real field you want for cut:

df -h /dev/sda2 | grep sda | tr -s " " " " | cut -d" " -f4

Alternatively, newer grep supports outputing only a partial match and you can use that in combination with a bash trick:

df -h /dev/sda2 | grep -o '[^[:space:]]*G' | cut -d$'\n' -f3

The regex could be safer, but this will find all the size fields and output them one per line, while cut selects the second.

Answer 3

All other answers here are great, but if you use Bash, there is no need to use external programs such as awk, sed, grep, cut etc.

The following line will do what you want:

{ read; read -r _ _ _ av _; } < <(df -h /dev/sda1)

"$av" will be the available size on /dev/sda1

If you want to use only the numeric part of "$av" ( e.g 123 in 123G ), you can use Parameter Expansion to trim the irrelevant part like that:

ir="${av##*[0-9]}"; echo "${av%$ir}"

or just "${av%?}" if you are sure that the suffix of "$av" is only one letter.

Answer 4

If it doesn't have to be grep/cut, you may be able to get the same information using stat. In filesystem mode, %a is number of free blocks and %s blocksize, so %a * %s is the free space in bytes, and you can do math to your liking with it to break it down to a more suitable unit of your choice, for example:

echo $((`stat -f -c "%a*%s" /media/windows/`/1024/1024/1024))GiB