Show difference between two number

Shell Programming and Scripting
1

Hi,

I would like to show the difference between two numbers. For example.

input.txt

1 7
2 10
0 0
6 7

I would like a third field showing the difference between the numbers as below:

ouput.txt

1 7 6
2 10 8
0 0 0
6 7 1

How do I do this?

Thanks,

2

Is this homework?

What have you tried so far?

Which OS; shell, machine etc...

3 
cat inputfile | while read a b
do
c=`expr $a - $b`
echo $a $b $c
done
4

Using Contos 6.4, bash shell on VM.

Amit, this works thanks.

5

Try :

$ awk '{print $0,$2-$1}' file

$ awk '$0 = $0 FS $2-$1' file