shell ---- 嵌套循环

嵌套循环

[root@localhost mnt]# cat qt.sh
#!/bin/bash
for ((a=1;a<=3;a++))
do 
    echo "Starting outside loop: $a"
    for ((b=1;b<=3;b++))
    do
        echo "Inside loop: $b"
    done
done 

效果如下：

[root@localhost mnt]# sh qt.sh 
Starting outside loop: 1
Inside loop: 1
Inside loop: 2
Inside loop: 3
Starting outside loop: 2
Inside loop: 1
Inside loop: 2
Inside loop: 3
Starting outside loop: 3
Inside loop: 1
Inside loop: 2
Inside loop: 3

练习：9*9乘法表

[root@localhost mnt]# cat 99.sh 
#!/bin/bash
for ((a=1;a<=9;a++))              或者for a in $(seq 9)
do 
   for ((b=1;b<=a;b++))           或者for b in $(seq $a)
   do   
	echo -ne "$a*$b=$(($a*$b))\t"
   done
   echo -e "\n"
done

[root@localhost mnt]# sh 99.sh 
1*1=1	

2*1=2	2*2=4	

3*1=3	3*2=6	3*3=9	

4*1=4	4*2=8	4*3=12	4*4=16	

5*1=5	5*2=10	5*3=15	5*4=20	5*5=25	

6*1=6	6*2=12	6*3=18	6*4=24	6*5=30	6*6=36	

7*1=7	7*2=14	7*3=21	7*4=28	7*5=35	7*6=42	7*7=49	

8*1=8	8*2=16	8*3=24	8*4=32	8*5=40	8*6=48	8*7=56	8*8=64	

9*1=9	9*2=18	9*3=27	9*4=36	9*5=45	9*6=54	9*7=63	9*8=72	9*9=81