Bash Multiplying Decimal to int

Question

I read price from user input. When i multiply the input with int like this

T="$((PRICE*QTY))"|bc; gives line 272: 12.00: syntax error: invalid arithmetic operator (error token is ".00") or .50

depending on user input. How do i multiply these two variables and get a total with 2 decimal points?

Answer 1

T="$(echo "$PRICE*$QTY" | bc)"

Answer 2

var=$(echo "scale=2;$PRICE*$QTY" |bc)

You can also use awk

awk -vp=$PRICE -vq=$QTY 'BEGIN{printf "%.2f" ,p * q}'

Answer 3

this works:

PRICE=1.1
QTY=21
RES=$(echo "scale=4; $PRICE*$QTY" | bc)
echo $RES

Answer 4

First, trying to do floating-point arithmetic with bc(1) without using the -l flag is bound to give you some funny answers:

sarnold@haig:~$ bc -q
3.5 * 3.5
12.2
sarnold@haig:~$ bc -q -l
3.5 * 3.5
12.25

Second, the $((...)) is an attempt to do arithmetic in your shell; neither my bash nor dash can handle floating point numbers.

If you want to do the arithmetic in your shell, note printf(1) as well as (probably) your shell's built-in printf function. If you want to do the arithmetic in bc, note the special variable scale.