Math in Bash

Calculating expression

Run (( expression ))

x=1
y=2
(( result = x + y ))
echo $result

To evaluate the expression directly

echo "$((x+y)) is sum of x and y"
echo "$((x-y)) is the difference of x and y"
echo "$((x*y)) is the product of x and y"
echo "$((x/y)) is the quotient of x and y"
echo "$((x%y)) is the reminder of x and y"

Declare integer type variable in bash

declare -i ivar

This command will make the ivar variable to hold only integer values

:::info

The Best Practice to write expression

(( ivar = x + y )) this is the best way

ivar=$(( x + y )) :::

Using read command to input integers

Decimal number in bash

:::info Bash does not know the decimals :::

Using bc command bc = basic calculator

Using awk to evaluate expression

If we have a file like

2
3
4
4
5
3
4
5
6

Then to sum up the values

awk '{ sum += $1 } END { print sum}' file

Print only first column

awk '{print $1}' filename

Changing the delimiter using -F