1.判斷輸入是否是數字，並且輸出簡單圖形

#!/bin/bash
read -p "input a num: " num
#判斷輸入是否是數字，直到輸入正確數字為止
flag=true
while $flag
do
if [ -n "$num" ];then
   test=$(echo "$num"|sed 's/[0-9]//g')
   if [ -z "$test" ];then
   flag=false   
   fi
fi
[ "$flag" == "false" ] || read -p "input correct num: " num
done

for (( i=1;i<=$num;i++ ))
  do 
   for j in $(seq 1 $i)
     do
     echo -n "*"
     done
   echo
  done

echo "############"

for (( i=$num;i>=1;i-- ))
  do 
   for j in $(seq 1 $i)
     do
     echo -n "*"
     done
   echo
  done
 

2.測試結果：