BASH Scripting: Cutting specific info from df command

mcgregor · 04-19-2011, 10:38 AM

Hello. I'm relatively new to Bash scripting. I have to create a table that lists specific things from the output of the df command.
It has to sort of look like this:
Filesystem Mounted Size Free Space
/dev/sda1 / 20G 9.7

and so on so forth.

I tried
df -h | tr -s " " | cut -f1 -d " "
but that gives me
/dev/sda1
/dev/sda1
and so on so forth

I understand that the cut command is seeing each column of info as one field. Is there a way around this? I need to cut each piece of info for one line
so
echo -e " $( df -h | tr -s " " | cut -f1 -d " ") \t $( df -h | tr -s " " | cut -f2 -d " ") \t
etc etc etc

Now here's the kicker. I can't use awk or sed. In my assignment, we are specifically forbidden to use awk or sed, so this implies to me that there is a way to do it. Hopefully this is enough information to make sense of what I need help with.

grail · 04-19-2011, 10:50 AM

Well I guess the first question would be do you have to use cut?
Also, how are you planning on getting data from each row?

Are you going to feed the information into a loop? If so, you could get rid of cut and tr all together.

And finally, yes awk and sed would make short work of this problem

mcgregor · 04-19-2011, 10:58 AM

Well I just assumed I would cut to get specific info from df. I want to try and echo each specific piece, in an specific order, instead of echoing the whole column, which is what's happening right now. I need to isolate each piece

It's got to look sort of like a table that unfortunately doesn't look like the table of the df command. So I just assumed this meant that I have to cut specific info.

mcgregor · 04-19-2011, 11:25 AM

Code:

df -h | grep ^/dev | tr -s " " | while read next
do
	device=$(echo $next | cut -f 1 -d " ")
	mntpoint=$(echo $next | cut -f 6 -d " ")
	size=$(echo $next | cut -f 2 -d " ")
	freespace=$(echo $next | cut -f 4 -d " ")
	echo -e "$device \t $mntpoint \t $size \t $freespace"
done

Apparently this is the answer. My teacher just gave it to me. Ugh. I've spent hours on this and I was going the wrong away about it entirely

grail · 04-19-2011, 11:46 AM

Well that is an answer. Personally not my choice as later when you wish to use a variable inside the loop and then report on it later, the above format will fail

Plus why not just use the read part of the loop to do all the work for you

Code:

#!/bin/bash

(

echo "Filesystem|Mounted|Size|Free Space"

while read -r device size _ freespace _ mntpoint
do
    [[ $device =~ ^/dev ]] || continue
    echo "$device|$mntpoint|$size|$freespace"
done< <(df -h)

) | column -t -s "|"