Calculate difference of numbers in two files

Question

Say I have two files where there is one number per line

File 1      file 2
0.12        0.11     
0.121       0.454 
....        .... 

I want to create file or output difference between each number on to the screen, so that result looks like

 0.0099
-0.333
 ......

You can use bash/awk/sed

Answer 1

awk

awk '{getline t<"file1"; print $0-t}' file2  #file2-file1

Explanation: getline t <"file1" gets a line from file1 and puts its value to variable t. $0 is the current record of file2 that awk is processing. the rest is just subtraction and printing the result out.

Bash

exec 4<"file1"
while read -r line
do
    read -r s <&4
    echo "${line}-${s}" | bc
done <"file2"
exec >&4-

Answer 2

# cat f1
0.12
0.121
# cat f2
0.11     
0.454

# pr -m -t -s\  f1 f2 | gawk '{print $1-$2}'
0.01
-0.333

Answer 3

Following shows how to get file1 - file2

$ cat file1
0.12
0.43
-0.333

$ cat file2
-0.1
-0.2
0.2

$ paste file1 file2 | awk '{print $1 - $2}'
0.22
0.63
-0.533

Answer 4

Bash:

paste file1 file2 | while read a b ; do 
  echo "$a - $b" | bc
done

Answer 5

paste -d - num1 num2 | bc

Edit:

This version properly handles negative numbers:

yes '-' | head -n $(wc -l < num1) | paste -d ' ' num1 - num2 | bc