shell脚本中的case条件语句介绍和使用案例

case "变量" in
    值1)
        指令1...
    ;;
    值2)
        指令2...
    ;;
    *）
        指令3...
esac

case "找工作条件" in
    给的钱多)
        给你工作...
    ;;
    给股份)
        给你工作...
    ;;
    有发展前景)
        可以试试...
    ;;
    *)
        bye bye !!
esac

[root@shell scripts]# cat num.sh 
#!/bin/bash

#create by guoke
#function number input

read -p "please input a number：" num  #打印信息提示用户输入，输入信息赋值给num变量

case "$num" in
    1)
        echo "The num you input is 1"
    ;;
    [2-5])
    　　echo "The num you input is 2-5"
    ;;
    [6-9])
    　　echo "The num you input is 6-9"
    ;;
    *)
    　　echo "please input number[1-9] int"
   　　 exit;
esac

[root@shell scripts]# sh num.sh 
please input a number：1
The num you input is 1
[root@shell scripts]# sh num.sh 
please input a number：3
The num you input is 2-5
[root@shell scripts]# sh num.sh 
please input a number：4
The num you input is 2-5
[root@shell scripts]# sh num.sh 
please input a number：8
The num you input is 6-9
[root@shell scripts]# sh num.sh
please input a number：a
please input number[1-9] int

[root@shell scripts]# cat menu.sh 
#!/bin/bash

#create by guoke
#function print menu

RED_COLOR='\E[1;31m'
GREEN_COLOR='\E[1;32m'
YELLOW_COLOR='\E[1;33m'
BLUE_COLOR='\E[1;34m'
RES='\E[0m'

echo ' #使用echo打印菜单
#############################
    1.banana
    2.apple
    3.pear
    4.cherry
#############################
'

read -p "please select a num：" num

case "$num" in
    1)
    　　echo -e "${YELLOW_COLOR} banana ${RES}"
    ;;
    2)
    　　echo -e "${RED_COLOR} apple ${RES}"
    ;;
    3)
    　　echo -e "${GREEN_COLOR} pear ${RES}"
    ;;
    4)
    　　echo -e "${BLUE_COLOR} cherry ${RES}"
    ;;
    *)
    　　echo "please input {1|2|3|4}"
esac

cat<<-EOF
===============================
    1.banana
    2.apple
    3.pear
    4.cherry
===============================
EOF

[root@shell scripts]# sh menu.sh 

#############################
    1.banana
    2.apple
    3.pear
    4.cherry
#############################

please select a num：
please input {1|2|3|4}

#!/bin/bash
yum install  gcc  pcre pcre-devel wget openssl  openssl-devel.x86_64  -y  
mkdir -p /home/demo/tools
cd /home/demo/tools/
wget  -q http://nginx.org/download/nginx-1.6.3.tar.gz
useradd  nginx -s /sbin/nologin -M
tar  xf nginx-1.6.3.tar.gz 
cd nginx-1.6.3/
./configure  --user=nginx --group=nginx   --prefix=/application/nginx --with-http_stub_status_module --with-http_ssl_module
make
make install
ln -s /application/nginx-1.6.3 /application/nginx/  #做软连接
/application/nginx/sbin/nginx  -t   #检查语法
/application/nginx/sbin/nginx       #启动服务

[root@shell init.d]# chmod +x /etc/init.d/nginxd
[root@shell init.d]# cat nginxd 
#!/bin/bash
#chkconfig: 2345 40 98   #设定2345级别，开机第40位启动脚本，关机第98位关闭脚本

#create by guoke
#email:1075792988@qq.com
#function nginx start scripts

[ -f /etc/init.d/functions ] && source /etc/init.d/functions  #引入系统函数库

PIDFILE=/application/nginx/logs/nginx.pid  #定义PID文件路径
NGINX=/application/nginx/sbin/nginx  #定义启动命令路径

value(){  #定义返回值函数
    RETVAL=$?
    if [ $RETVAL -eq 0 ];then
    　　action "Nginx is $1" /bin/true
    else
    　　action "Nginx is $1" /bin/true
    fi
}

start(){ #定义启动函数
    if [ -f $PIDFILE ];then  #判断PIDFILE存不存在，存在就打印运行，否则就启动
    　　echo "Nginx is running"
    else
    　　$NGINX
    　　value start #调用返回值函数
    fi
}

stop(){ #定义停止函数
    if [ ! -f $PIDFILE ];then #也是通过判断PID文件是否存在然后进行相关操作
    　　echo "Nginx not running"
    else
    　　$NGINX -s stop
    　　value stop
    fi
}

reload(){ #定义重启函数
    if [ ! -f $PIDFILE ];then
    　　echo "not open $PIDFILE no such directory"
    else
    　　$nginx -s reload
    　　value reload
    fi
}

case "$1" in  #使用case接收脚本传参的字符串
    start)  #如果第一个参数为start，调用start函数
    　　start
    ;;
    stop)   #如果第一个参数为stop，调用stop函数
    　　stop
    ;;
    reload)
    　　stop
    　　sleep 1
    　　start
    ;;
    *)
    　　echo "USAGE:$0 {stop|start|reload}"
    　　exit 1
esac

[root@shell init.d]# sh nginx stop
Nginx is stop                                              [  OK  ]
[root@shell init.d]# sh nginx start
Nginx is start                                             [  OK  ]
[root@shell init.d]# sh nginx reload
Nginx is stop                                              [  OK  ]
Nginx is start                                             [  OK  ]

1.首先做好ssh key验证登录
2.实现远程连接菜单选择脚本
3.利用Linux信号防止用户在跳板机上操作
4.用户登录后就调用脚本

[demo@shell ~]$ ssh-keygen  -t dsa -P "" -f ~/.ssh/id_dsa  
Generating public/private dsa key pair.
Enter file in which to save the key (/home/demo/.ssh/id_dsa): 
Created directory '/home/demo/.ssh'.
Your identification has been saved in /home/demo/.ssh/id_dsa.
Your public key has been saved in /home/demo/.ssh/id_dsa.pub.
The key fingerprint is:
SHA256:BTFfcC2hMKBzuZeUYylC3qgza7z4X6j3RBlwq8Beoak demo@shell
The key's randomart image is:
+---[DSA 1024]----+
|    + o.*...+o   |
| . = B o O +. .  |
|  = B B * +  .   |
| o + = B +       |
|E = . + S        |
| . + o .         |
|  + . o          |
| o o.o           |
|..+o...          |
+----[SHA256]-----+
#命令说明：一键生成密钥，不用按回车。-t：指定要创建的密钥类型，-P：提供旧密码，空表示不需要密码，-f：指定位置

#将公钥拷贝到其他服务器的demo用户
[demo@shell ~]$ ssh-copy-id -i .ssh/id_dsa.pub "demo@192.168.86.129"
[demo@shell ~]$ ssh-copy-id -i .ssh/id_dsa.pub "demo@192.168.86.130"
[demo@shell ~]$ ssh-copy-id -i .ssh/id_dsa.pub "demo@192.168.86.131"

[root@shell scripts]# cat tiaobanji.sh 
#!/bin/bash

trapper(){  #定义屏蔽信号函数
    trap  '' INT QUIT TSTP TERM HUB
}

menu(){ #定义菜单列表函数
    cat<<-EOF #加-后面的EOF就可以不用顶格
==============Host List==============
    1) 192.168.86.129
    2) 192.168.86.130
    3) 192.168.86.131
    4) 192.168.86.132
    5) exit
=====================================
    EOF
}

USER=demo

host(){ #定义主机列表函数
    case "$1" in
    1)
        ssh $USER@192.168.86.129
    ;;
    2)
        ssh $USER@192.168.86.130
    ;;
    3)
        ssh $USER@192.168.86.131
    ;;
    4)
        ssh $USER@192.168.86.132
    ;;
    5)
        exit
esac
}

main(){ #定义主函数
    while : #while循环，一直循环
    do
        trapper #调用trapper函数
        clear  #清屏
        menu #调用菜单函数
        read -p "please select a num：" num #获取用户输入
        host $num #调用主机列表函数和传入的参数，进行远程登录
    done
}
main #调用主函数

[root@shell ~]# cd /etc/profile.d/
[root@shell profile.d]# cat jump.sh 
#!/bin/bash

[ $UID -ne 0 ] && . /scripts/tiaobanji.sh

==============Host List==============
1) 192.168.86.129
2) 192.168.86.130
3) 192.168.86.131
4) 192.168.86.132
5) exit
=====================================
please select a num：1  #进行选择
Last login: Tue Mar 31 23:48:33 2020 from 192.168.86.128
[demo@mysql ~]$ 

1.禁止跳板机可以从外网IP进行登录，只能从内网IP登录
2.其他服务器也限制只能内网IP登录，同时禁止root登录，做完ssh key认证，将密码登录禁止，通过免密码登录到其他服务器