preparation of an isosceles right angle trapezoidal square shell receiving a digital input by the user

triangle

#!/bin/bash
read -p 'input number: ' a
for ((i=1;i<=$a;i++));do
	for ((j=((2*${a}-2*${i}));j>=0;j--));do
		echo -e " \c"
	done
	for ((k=1;k<=((2*${i}-1));k++));do
		echo -e " *\c"
	done
echo
done

square

#!/bin/bash
read -p 'input: ' a
for ((i=1;i<=$a;i++));do
	for ((j=1;j<=$a;j++));do
	echo -e "■ \c"
	done
echo
done

Trapezoidal

read -p 'input: ' a b
for ((i=$a;i<=$b;i++));do
	for ((j=1;j<=$i;j++));do
		echo -e "*\c"
	done
echo
done