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case 模式匹配
一、case语法结构
case 变量名 in
模式1)
命令序列1
;;
模式2)
命令序列2
;;
模式3)
命令序列3
;;
*）
无匹配后命令序列
esac
在某种意义上，case语句是if语句的简洁版，case语句适合做字符串模式匹配，如果不同的字符值对应不同的功能则用case语句实现，case无法做比较以及测试命令，最后一个模式可以省略;;
command -v 命令用来测试是否是一个命令看$?返回值即可
1.1根据系统版本匹配yum源文件
#!/bin/bash
yum_server=192.168.81.250
os_version=$(cat /etc/redhat-release |awk '{print $(NF-1)}'| awk -F '.' '{print $1"."$2}')
[ -d /etc/yum.repos.d/bak ] || mkdir -p /etc/yum.repos.d/bak
mv /etc/yum.repos.d/* /etc/yum.repos.d/bak &>/dev/null
case "$os_version" in
"7.6")
cat > /etc/yum.repos.d/centos7u6.repo <<-EOF
[centos7u6]
name=centos7u6
baseurl=file:///media
enabled=1
gpgcheck=0
EOF
echo "$os_version yum config finish...."
;;
"6.5")
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-6.repo
echo "$os_version yum config finish...."
;;
"5.4")
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-5.repo
echo "$os_version yum config finish...."
;;
*)
echo "error os_version"
esac
echo "finish.."
1.2删除用户，根据输入的字符确认是否删除
#!/bin/bash
-------------------if实现-----------------
read -p "please input a delete username: " user
id $user &>/dev/null
if [ $? -ne 0 ];then
echo "no such user: $user"
exit 1 //设置退出状态码
fi
read -p "are you sure delete: $user [y/n]" action
if [ "$action" = y -o "$action" = "yes" -o "$action" = "Y" -o "$action" = "YES" ];then
userdel -r $user &>/dev/null
echo "$uer is del..."
else
echo "you is quit"
fi
-------------------------case实现-----------------
read -p "please input a delete username: " user
id $user &>/dev/null
if [ $? -ne 0 ];then
echo "no such user: $user"
exit 1
fi
read -p "are you sure delete: $user [y/n]" action
case $action in
y|Y|yes|YES)
userdel -r $user &>/dev/null
echo "$user is del..."
;;
*)
echo "you is quit"
esac
1.3测试某个文件是否是一个命令
#!/bin/bash
command1=/bin/date
if command -v $command1 &>/dev/null;then
:
else
echo " $command is not keywords"
fi
1.4利用case+if实现批量创建用户
#!/bin/bash
read -p "please input prefix: " prefix
if [ -z $prefix ];then
echo "error prefix"
exit 1
fi
read -p "please input create num: " num
if [[ ! $num =~ ^[0-9]+$ ]];then
echo "error num"
exit 2
fi
read -p "are you sure create {prefix+num} user[y/n]: " action
case $action in
y|Y|yes|YES)
echo "begin create....."
for i in `seq $num`
do
user=$prefix$i
useradd $user &>/dev/null
if [ $? -eq 0 ];then
echo "123" | passwd --stdin $user &>/dev/null
fi
echo "$user is add....."
done
;;
n|N|no|NO)
echo "scripts is quit...."
esac
1.4利用case+if实现批量删除用户
#!/bin/bash
read -p "please input prefix: " prefix
if [ -z $prefix ];then
echo "error prefix"
exit 1
fi
read -p "please input delete num: " num
if [[ ! $num =~ ^[0-9]+$ ]];then
echo "error num"
exit 2
fi
read -p "are you sure delete {prefix+num} user[y/n]: " action
case $action in
y|Y|yes|YES)
echo "begin delete....."
for i in `seq $num`
do
user=$prefix$i
userdel -r $user &>/dev/null
echo "$user is del....."
done
;;
n|N|no|NO)
echo "scripts is quit...."
esac
1.5case实现编译安装软件
#!/bin/bash
###############################################################################################
# #
# case编译安装工具箱 jxl--20200225 #
# #
###############################################################################################
tools_dir=/software
apache_tools_dir=/software/httpd-2.2.17.tar.gz
mysql_tools_dir=/software/mysql-5.5.22.tar.gz
cmake_tools_dir=/software/cmake-2.8.6.tar.gz
nginx_tools_dir=/software/nginx-1.6.0.tar.gz
echo -e "\033[33m begin checking software...\033[0m"
yum list installed | grep 'gcc-c++' &>/dev/null
if [ $? -ne 0 ];then
read -p "system not gcc,do you install gcc-c++? [y|n]: " action
case $action in
y|Y)
yum -y install gcc-c++
if [ $? -eq 0 ];then
echo -e "\033[32m gcc-c++ is installed... \033[0m"
fi
;;
n|N)
echo -e "\033[31m no gcc-c++ not install tools... \033[0m"
echo -e "\033[31m scripts is quit... \033[0m"
exit 1
;;
esac
fi
echo -e "\033[31m Can install the tool:[httpd|mysql|nginx] \033[0m"
read -p "please input install tool: " tool
case $tool in
httpd)
read -p "are you sure install apache_httpd [y|n]: " action_httpd
if [ "$action_httpd" = "y" -o "$action_httpd" = "yes" ];then
yum -y remove httpd
tar xvf $apache_tools_dir -C $tools_dir
cd $tools_dir/httpd-2.2.17
./configure --prefix=/usr/local/httpd --enable-so --enable-rewrite --enable-charset-lite --enable-cgi && make && make install
ln -s /usr/local/httpd/bin* /usr/local/bin &>/dev/null
cp /usr/local/httpd/bin/apachectl /etc/init.d/httpd
sed -i -e '1a # chkconfig:35 85 21' /etc/init.d/httpd
sed -i -e '2a # description:Startup script for the Apache HTTP Server' /etc/init.d/httpd
systemctl start httpd
systemctl enable httpd
netstat -lnpt | grep httpd
if [ $? -eq 0 ];then
echo -e "\033[32m httpd installed....\033[0m"
fi
elif [ "$action_httpd" = "n" -o "$action_httpd" = "no" ];then
echo -e "\033[31m scripts is quit... \033[0m"
exit 1
else
echo -e "\033[31m error action \033[0m"
exit 2
fi
curl -I 127.0.0.1 &>/dev/null
if [ $? -eq 0 ];then
echo -e "\033[32m web page is ok...\033[0m"
fi
;;
mysql)
read -p "are you sure install mysql [y|n]: " action_mysql
if [ "$action_mysql" = "y" -o "$action_mysql" = "yes" ];then
yum -y remove mariadb
yum -y install ncurses-devel
tar xvf $cmake_tools_dir -C $tools_dir
cd $tools_dir/cmake-2.8.6
./configure && make && make install
tar -xvf $mysql_tools_dir -C $tools_dir
cd $tools_dir/mysql-5.5.22
cmake -DCMAKE_INSTALL_PREFIX=/usr/local/mysql -DDEFAULT_CHARSET=utf8 -DDEFAULT_COLLATION=utf8_general_ci -DWICH_EXTRA_CHARSETS=all -DSYSCONFDIR=/etc && make &&make install
\cp -rf support-files/my-medium.cnf /etc/my.cnf
\cp -rf support-files/mysql.server /etc/init.d/mysqld
chmod +x /etc/init.d/mysqld
ln -s /usr/local/mysql/bin/* /usr/local/bin &>/dev/null
groupadd mysql &>/dev/null
useradd -M -s /sbin/nologin -g mysql mysql &>/dev/null
chown -R mysql:mysql /usr/local/mysql
/usr/local/mysql/scripts/mysql_install_db --basedir=/usr/local/mysql/ --datadir=/usr/local/mysql/data/ --user=mysql
/etc/init.d/mysqld start
netstat -lnpt | grep mysql
if [ $? -eq 0 ];then
echo -e "\033[32m mysqld installed...\033[0m"
fi
elif [ "$action_mysql" = "n" -o "$action_mysql" = "no" ];then
echo -e "\033[31m scripts is quit... \033[0m"
exit 1
else
echo -e "\033[31m error action... \033[0m"
exit 2
fi
;;
nginx)
read -p "are you sure install mysql [y|n]: " action_nginx
if [ "$action_nginx" = "y" -o "$action_nginx" = "yes" ];then
yum -y install openssl-devel zlib-devel pcre-devel
tar -xvf $nginx_tools_dir -C $tools_dir
cd $tools_dir/nginx-1.6.0
./configure --prefix=/usr/local/nginx --with-http_ssl_module && make && make install
netstat -lnpt | grep 80
if [ $? -eq 0 ];then
echo -e "\033[32m port 80 is used...\033[0m"
echo -e "\033[33m begin update port is 8888!\033[0m"
sed -i 's/80;/8888;/' /usr/local/nginx/conf/nginx.conf
if [ $? -eq 0 ];then
echo -e "\033[33m port is 8888...\033[0m"
fi
fi
ln -s /usr/local/nginx/sbin/* /usr/local/sbin &>/dev/null
nginx
netstat -lnpt | grep nginx
if [ $? -eq 0 ];then
echo -e "\033[32m nginx installed...\033[0m"
fi
elif [ "$action_nginx" = "n" -o "$action_nginx" = "no" ];then
echo -e "\033[31m scripts is quit... \033[0m"
exit 1
else
echo -e "\033[31m error action... \033[0m"
exit 2
fi
;;
*)
echo -e "\033[31m The tool is still in development...\033[0m"
esac
1.6case实现简单的跳板机
跳板机适用场景：
1.业务服务器不允许直接连接，通过跳板机进行连接
2.业务服务器不允许root用户登录
跳板机原理
由客户端登录到跳板机服务器，跳板机服务器根据用户输入的ip远程连接对应的应用服务器，客户端不能直接与应用服务器直连，所有主机准备远程连接时使用的账号密码，并设置为密码验证或者密钥验证
此案例需求：
1.做出一个服务器列表
2.根据用户的输入判断去连接哪一台服务器
3.用户连到跳板机服务器就已经将脚本运行好
4.连接进去后不允许退出
#!/bin/bash
clear
trap "" INT HUP OUIT TSTP
while :
do
cat <<-EOF
+---------------------------------------------------------+
| jumpserver |
| 1.192.168.81.210 |
| 2.192.168.81.211 |
| 3.192.168.81.212 |
| 4.192.168.81.213 |
+---------------------------------------------------------+
EOF
echo -en "\e[33m please input connection host: \e[0m"
read host
case $host in
1)
ssh jxl@192.168.81.210
;;
2)
ssh jxl@192.168.81.211
;;
3)
ssh jxl@192.168.81.212
;;
4)
ssh jxl@192.168.81.213
;;
"")
;;
*)
echo "The host does not exist"
esac
done
1.7case实现系统管理工具箱
#!/bin/bash
menu(){
cat <<-EOF
+------------------------------------------------------------+
| 系统工具箱 |
| h.help |
| b.磁盘分区情况 |
| d.磁盘使用情况 |
| m.内存使用情况 |
| u.系统负载情况 |
| t.CPU使用情况 |
| q.exit |
+------------------------------------------------------------+
EOF
}
clear
while :
do
menu
echo -en "\e[33m Please choose to use tool: \e[0m"
read tools
case $tools in
h)
echo "这是一个系统管理工具箱，可以根据所需选择对应的工具"
menu
;;
b)
lsblk
;;
d)
df -hT
;;
m)
free -g
;;
u)
uptime
;;
t)
top
;;
q)
exit
;;
"")
;;
*)
echo -e "\e[31m error option \e[0m"
esac
done
