shell输出星星三角阵

shell输出星星三角阵
要求输出

程序如下

#!/bin/bash

rows=4

for (( i=1; i<=rows; i++ ))
do
  for (( j=1; j<=i; j++ ))
  do
    echo -n "* "
  done
  echo
done
for (( i=1; i<=rows; i++ ))
do
  for (( j=1; j<=rows-i; j++ ))
  do
    echo -n "* "
  done
  echo
done