shell简单使用(二)循环

记录几个循环相关的简单例子

1. 等待输入预期的内容

#!/bin/bash

until [ "$yn" == "yes" -o "$yn" == "YES" ]
do
    read -p "Please input yes/YES to stop this progras: " yn
done

echo "OK! you input the correct answer. "

等待输入预期的内容才退出

也可用while实现

2. 多数字求和

　while实现

i=0
s=0

while [ "$i" != "100" ]
do
    i=$(($i + 1))
    s=$(($s + $i))
done

echo "The result of '1+2+..+100' is ==> $s "

用for实现

#!/bin/bash

s=0

read -p "Please input a number, I will count for 1+2+3+...+your_input: " nu
for (( i=1; i<=$nu; i=i+1 ))
do
    s=$(($s + $i))
done

echo "The result of '1+2+..+100' is ==> $s "

执行结果

3. 字符串处理

for循环对文件名逐个处理

#!/bin/bash

for var in `ls`
do
    echo $var
done

执行结果如下

for循环处理用户信息

#!/bin/bash

users=$(cut -d : -f1 /etc/passwd)
for username in $users
do
    id $username
    finger $username
done

 for循环查找指定ip地址的连通性

#!/bin/bash

network="192.168.1"

for sitenu in $(seq 97 110)
do
    ping -c 1 -w 1 ${network}.${sitenu} &> /dev/null && result=0 || result=1
    if [ "$result" == 0 ]; then
        echo "Server ${network}.${sitenu} is UP"
    else
        echo "Server ${network}.${sitenu} is DOWN"
    fi
done

执行结果：