shell学习笔记：控制结构

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if结构：

read -p "Please input (Y/N): " yn

if [ "$yn" == "Y" -o "$yn" == "y" ]; then
    echo "OK, continue"
elif [ "$yn" == "N" -o "$yn" == "n" ]; then
    echo "Oh, interrupt!"
else
    echo "I don't know what your choice is"
fi=====================================================case结构：case $1 in 
  "hello")    echo "Hello, how are you ?"    ;;  "")    echo "You MUST input parameters, ex> {$0 someword}"    ;;  *)   # 其实就相当於万用字节，0~无穷多个任意字节之意！    echo "Usage $0 {hello}"    ;;esac======================================================while 结构：while [ "$yn" != "yes" -a "$yn" != "YES" ] #当条件为真时执行循环do    read -p "Please input yes/YES to stop this program: " yndone
echo "OK! you input the correct answer."
=======================================================
s=0  # 这是加总的数值变量i=0  # 这是累计的数值，亦即是 1, 2, 3....while [ "$i" != "100" ]do    i=$(($i+1))   # 每次 i 都会添加 1     s=$(($s+$i))  # 每次都会加总一次！done
echo"The result of '1+2+3+...+100' is ==> $s"=======================================================


until结构
until [ "$yn" == "yes" -o "$yn" == "YES" ] #当条件为真时退出循环do    read -p "Please input yes/YES to stop this program: " yndone
echo "OK! you input the correct answer."======================================================for结构：

for animal in dog cat elephant
do
    echo "There are ${animal}s.... "
done=====================================================network="192.168.1"              # 先定义一个网域的前面部分！for sitenu in $(seq 1 100)       # seq 为 sequence(连续) 的缩写之意do    # 底下的程序在取得 ping 的回传值是正确的还是失败的！        ping -c 1 -w1 ${network}.${sitenu} &> /dev/null && result=0 || result=1    # 开始显示结果是正确的启动 (UP) 还是错误的没有连通 (DOWN)        if [ "$result" == 0 ]; then
            echo "Server ${network}.${sitenu} is UP."
        else
            echo "Server ${network}.${sitenu} is DOWN."
        fi
done====================================================

# 1. 先看看这个目录是否存在啊？
read -p "Please input a directory: " dir
if [ "$dir" == "" -o ! -d "$dir" ]; then
    echo"The $dir is NOT exist in your system."    exit 1
fi# 2. 开始测试文件罗～filelist=$(ls $dir)        # 列出所有在该目录下的文件名称for filename in $filelistdo    perm=""    test -r "$dir/$filename" && perm="$perm readable"    test -w "$dir/$filename" && perm="$perm writable"    test -x "$dir/$filename" && perm="$perm executable"
    echo "The file $dir/$filename's permission is $perm "
done====================================================C语言方式：(双小括号方式--单小括号是执行命令)read -p "Please input a number, I will count for 1+2+...+your_input: " nus=0
for (( i=1; i<=$nu; i=i+1 ))do    s=$(($s+$i))done
echo"The result of '1+2+3+...+$nu' is ==> $s"=====================================================select 结构
echo "What is your favourite OS?"select var in "Linux" "Gnu Hurd" "Free BSD" "Other"; do  break;doneecho "You have selected $var"
该脚本的运行结果如下：
What is your favourite OS?1) Linux2) Gnu Hurd3) Free BSD4) Other#? 1You have selected Linux

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shell学习笔记：控制结构

select 结构

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