linux中while循環

 

1、

[root@rhel7pc1 test]# ls
test.sh
[root@rhel7pc1 test]# cat test.sh
#!/bin/bash
NUM=10
while [ $NUM -gt 0 ]      ## 循環條件 do
echo "$NUM xxxx"
let NUM--                  ## 循環變量的變化
done
[root@rhel7pc1 test]# bash test.sh
10 xxxx
9 xxxx
8 xxxx
7 xxxx
6 xxxx
5 xxxx
4 xxxx
3 xxxx
2 xxxx
1 xxxx

 

2、同上

[root@rhel7pc1 test]# ls
test.sh
[root@rhel7pc1 test]# cat test.sh
#!/bin/bash
NUM=10
while [ $NUM -gt 0 ]
do
echo "$NUM xxxx"
let NUM-=2
done
[root@rhel7pc1 test]# bash test.sh
10 xxxx
8 xxxx
6 xxxx
4 xxxx
2 xxxx

 

3、以交互方式決定循環次數

[root@rhel7pc1 test]# ls
test.sh
[root@rhel7pc1 test]# cat test.sh
#!/bin/bash
read -p "please input the loop times: " NUM
while [ $NUM -gt 0 ]
do
echo "$NUM xxxx"
let NUM-=1
done
[root@rhel7pc1 test]# bash test.sh
please input the loop times: 3
3 xxxx
2 xxxx
1 xxxx
[root@rhel7pc1 test]# bash test.sh
please input the loop times: 5
5 xxxx
4 xxxx
3 xxxx
2 xxxx
1 xxxx