详解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]# 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=$"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

[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 ~]$