一、条件语句 if

1.1、单分支

if [ 1 -eq 1 ];then
        echo "haha"
fi

1.2、双分支

if [ 1 -eq 2 ];then
        echo "haha"
else
        echo "shadan"
fi

1.3、多分支

if [ 1 -eq 2 ];then
        echo "haha"
elif [ 1 -eq 1 ];then
        echo "123"
else
        echo "shadan"
fi

脚本1,yum源，防火墙配置

#!/bin/bash
str=`cat /etc/redhat-release |awk '{print $4}'|awk -F '.' '{print $1}'`
version=0
mkdir /etc/yum.repos.d/bak &>/dev/null
mv /etc/yum.repos.d/* /etc/yum.repos.d/bak/ &>/dev/null
if [ $str == 7 ];then
    version=7
else
    version=6
fi
echo $version
if [ $version -eq  7 ];then
    #关闭防火墙及开机自启
    systemctl stop firewalld
    systemctl disable firewalld
    #关闭selinux
    setenforce 0
    sed -i 7s/enforcing/disabled/g /etc/selinux/config
    wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
    #配置yum源
    wget -O /etc/yum.repos.d/epel.repo http://mirrors.aliyun.com/repo/epel-7.repo
elif [ $version -eq 6 ];then
    #关闭防火墙及开机自启
    iptables -F
    service iptables stop
    chkconfig iptables off
    #关闭selinux
    setenforce 0
    sed -i 7s/enforcing/disabled/g /etc/selinux/config
    #配置yum源
    wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-6.repo
    wget -O /etc/yum.repos.d/epel.repo http://mirrors.aliyun.com/repo/epel-6.repo
else
    echo "please check your /etc/redhat-release file "
fi
yum clean all
yum makecache

二、条件语句 case

2.1、格式

case    变量  in  
    匹配条件1)                  
        命令序列    1
                ;;  
    匹配条件2)                  
        命令序列    2
                ;;  
    匹配条件3)                  
        命令序列    3
                ;;  
           *)                   
        ⽆匹配后命令列 
esac

脚本1，批量删除用户

#!/bin/bash
 while true
 do
    read -p "请输入你要删除的账户前缀>> " delname
    read -p "请输入你要删除的账户数量>> " delnum
    echo  "你将删除如下账户：
            用户前缀是: $delname
            用户数量是: $delnum"
    read -p "你确定要删除（y|yes/n|no）?" ch
    case $ch in
        y|yes)
            for i in `seq $delnum`
                do
                    username=$delname$i
                    id $username &>/dev/null
                        if [ $? -eq 0 ];then
                            userdel -r $username
                            echo "删除成功 $username"
                        else
                            echo "没有该用户 $username"
                        fi
                done
            break
            ;;
        n|no)
            echo "取消删除"
            exit 1
            ;;
        *)
            echo "错误输入，请重新输入"
    esac
done

脚本2，系统命令工具箱

#!/bin/bash
menu(){
cat << EOF
    =====================system info====================
                h、显示帮助命令
                f、显示磁盘分区
                d、显示磁盘挂载
                m、查看内存使用
                u、查看系统负载
                q、退出脚本
    =====================system info====================
EOF
}
menu
while true
do
read -p "请输入对应序号>> " ch
    case $ch in 
        h)
        clear
        menu
        ;;
        f|d)
        lsblk
        ;;
        m)
        free -h
        ;;
        u)
        uptime 
        ;;
        q)
        exit
        ;;
        *)
        echo "error input"
        
    esac
done

三、交互脚本expect

执行某些命令时，需要回答，例如 ssh登录 需要输入yes和密码

[root@localhost ~]# ssh root@100.100.100.101
The authenticity of host '100.100.100.101 (100.100.100.101)' can't be established.
ECDSA key fingerprint is SHA256:O84EC9RloVc32hoAxnpkn29AX9kM4z+xMgZ3h1CJkj8.
ECDSA key fingerprint is MD5:a8:2c:88:fd:64:2f:ad:8d:69:75:37:b9:19:2c:8c:57.
Are you sure you want to continue connecting (yes/no)? yes 
Warning: Permanently added '100.100.100.101' (ECDSA) to the list of known hosts.
root@100.100.100.101's password: 
Last failed login: Tue Jan 28 02:10:31 CST 2020 on tty1
There was 1 failed login attempt since the last successful login.
Last login: Mon Jan 27 22:23:10 2020

3.2 我们使用 expect 完成上述操作

!/bin/expect
spawn  ssh root@100.100.100.101
expect {
    "yes/no" {send "yes\r";exp_continue}
    "password" {send "123\r"}
}
interact 显示执行过程
expect "#" 当出现 # 号符执⾏行行如下命令 
    send "echo haha\r"
    send "exit\r"
expect eof

注意,不能使用 bash执行，而是赋予权限，使用 source 脚本名 或者 ./脚本名 执行

脚本，使用 expect 进行密钥对分发

#!/bin/bash
#获取当前网段可用ip
read -p "请输入网段..." ip_pre
rm -rf ip.txt &>/dev/null
for i in {1..254}
do
    {
    ip=$ip_pre.$i
    ping -c1 -w1 $ip >/dev/null
    if [ $? -eq 0 ];then
        echo "$ip"|tee -a ip.txt
   fi
}&
done
wait

#生成密钥对
if [ ! -f ~/.ssh/id_rsa ];then
        ssh-keygen -P "" -f ~/.ssh/id_rsa
fi

#使用expect分发密钥
while read line
do
        /usr/bin/expect <<-EOF
        spawn   ssh-copy-id     $line   -f
        expect  {
                "yes/no" {send  "yes\r";exp_continue}
                "password" {send "123\r"}
                }
        expect eof
        EOF
done<ip.txt