regex - Adding a leading zero to a float number in a bash script -

my script

#!/bin/bash echo -n "number 1 :"; read number1 echo -n "number 2 :"; read number2     jlh=$(echo $number1 + $number2 | bc -l | sed 's/^\./0./');     echo "your result : $number1 + $number2 = $jlh " 

if input number 1 -1 , , number 2 0.9, why result -.1.

i want show 0 this.

your result : -1 + 0.9 = -0.1 

how can it?

because consider case .nnn, not -.nnn, having minus - sign before:

with should work:

sed    -e 's/^\./0./'       -e 's/^-\./-0./'            start .         start -. 

all together;

jlh=$(echo $number1 + $number2 | bc -l | sed -e 's/^\./0./' -e 's/^-\./-0./');