流程控制之case语句
一 、语法
case 变量 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
二、 案例
案例1
[root@openvpn day3]# cat check_role.sh
#! /bin/bash
read -p "please input you name:" name
if [ -z "$name" ];then
name="default"
fi
case $name in
"root")
echo "管理员"
;;
"mm")
echo "普通"
;;
"default")
echo "默认用户"
;;
*)
echo "防客"
esac
案例2：编写nginx启动脚本
[root@egon shell]# cat nginx_stat.sh
#!/bin/bash
. /etc/init.d/functions
if [ $# -ne 1 ]
then
echo "USAGE $0 {start|stop|restart}"
exit 1
fi
if [ "$1" == "start" ]
then
action "start nginx" /bin/true
elif [ "$1" == "stop" ]
then
action "stop nginx" /bin/true
elif [ "$1" == "restart" ]
then
action "restart nginx" /bin/true
else
echo "USAGE $0 {start|stop|restart}"
exit 1
fi
[root@egon shell]# chmod +x nginx_stat.sh
[root@egon shell]# ./nginx_stat.sh start
start nginx [ 确定 ]
[root@egon shell]# ./nginx_stat.sh restart
restart nginx [ 确定 ]
[root@egon shell]# ./nginx_stat.sh
USAGE ./nginx_stat.sh {start|stop|restart}
案例3：编写nginx启动脚本
# 储备知识1
netstat -lntup|grep ":80\b" # \b锚定单词的结尾
# 储备知识2
action:打印一段信息并执行给定的命令，然后根据给定命令的执行的结果来调用 success,failure方法，确定最终显示的内容
[root@egon shell]# action "nginx start is" :
nginx start is [ 确定 ]
[root@egon shell]# action "nginx start is" /bin/true
nginx start is [ 确定 ]
[root@egon shell]# action "nginx start is" /bin/false
nginx start is [失败]
# 代码
[root@egon shell]# cat nginx_stat.sh
#!/bin/bash
. /etc/init.d/functions
args=$1
fun(){
[ $? -eq 0 ] && action "Nginx $args is " /bin/true || echo "Nginx $args is " /bin/false
}
case $1 in
start)
netstat -an | grep -i Listen | grep -q "\b80\b"
if [ $? -eq 0 ]
then
echo "Nginx is runing..."
else
/usr/sbin/nginx
fun
fi
;;
stop)
/usr/sbin/nginx -s stop
fun
;;
reload)
/usr/sbin/nginx -s reload
fun
;;
restart)
netstat -lntup|grep ":80\b" &>/dev/null
if [ $? -ne 0 ]
then
/usr/sbin/nginx
[ $? -eq 0 ] && echo "Nginx start is ok" || echo "Nginx start is failed"
else
/usr/sbin/nginx -s stop
[ $? -eq 0 ] && echo "Nginx stop is ok" || echo "Nginx stop is failed"
sleep 2
/usr/sbin/nginx
fun
fi
;;
status)
netstat -lntup|grep ":80\b" &>/dev/null
if [ $? -eq 0 ]
then
echo "Nginx is runing ..."
else
echo "Nginx is not runing ..."
fi
;;
*)
echo "Usage: $0 {start|stop|status|restart|reload}"
exit 2
esac
# 方式二
# 使用if判断，编写nginx启动脚本，支持stop|start|reload
[root@openvpn day3]# cat nginx.sh
#!/bin/bash
. /etc/init.d/functions
# nginx -s stop 停止
# nginx 启动
# nginx -s reload 重载
read -p "请输入操作模式（stop|start|reload）" nginx_start
if [[ $nginx_start == "start" ]];then
nginx
if [ $? -eq 0 ];then
action "Nginx启动成功" /bin/true
else
action "Nginx启动失败" /bin/false
fi
elif [[ $nginx_start == "stop" ]];then
nginx -s stop
if [ $? -eq 0 ];then
action "Nginx关闭成功" /bin/true
else
action "Nginx关闭失败" /bin/false
fi
elif [[ $nginx_start == "reload" ]];then
nginx -s reload
if [ $? -eq 0 ];then
action "Nginx重载成功" /bin/true
else
action "Nginx重载失败" /bin/false
fi
else
echo "输入的操作模式错误，请使用操作模式（stop|sta
fi
方式三：
使用case判断，编写nginx启动脚本，支持stop|start|reload
[root@openvpn day3]# cat nginx.case.sh
. /etc/init.d/functions
# nginx -s stop 停止
# nginx 启动
# nginx -s reload 重载
read -p "请输入操作模式（stop|start|reload）" nginx_start
case $nginx_start in
start)
nginx
case $? in
0)
action "Nginx启动成功" /bin/true
;;
*)
action "Nginx启动失败" /bin/false
;;
esac
;;
stop)
nginx -s stop
case $? in
0)
action "Nginx关闭成功" /bin/true
;;
*)
action "Nginx关闭失败" /bin/false
;;
esac
;;
reload)
nginx -s reload
case $? in
0)
action "Nginx重载成功" /bin/true
;;
*)
action "Nginx重载失败" /bin/false
;;
esac
;;
*)
echo "输入的操作模式错误，请使用操作模式（stop|start|reload）"
;;
esac
案例4：编写一个简易跳板机脚本
# 储备知识
Linux中断信号区别为：键入不同、对应操作不同、启用不同。
1、HUP中断信号：HUP中断信号的对应操作为让进程挂起，睡眠。同<Ctrl+X>
2、INT中断信号：INT中断信号的对应操作为正常关闭所有进程。同<Ctrl+C>
3、TERM中断信号 15：TERM中断信号的对应操作为正常的退出进程。
4、KILL中断信号 9：KILL中断信号的对应操作为强制关闭进程。
5、STOP 19暂停（同 Ctrl + Z）
6、CONT 18继续（与STOP相反， fg/bg命令）
7、TSTP中断信号：TSTP中断信号的对应操作为暂时停用进程。
# 代码
[root@egon shell]# cat jumpserver.sh
#!/bin/bash
cat<<EOF
1. BACKUP 192.168.15.41
2. WEB02 192.168.15.8
3. WEB03 192.168.15.9
EOF
trap "echo 不要乱按键盘,否则服务器将会爆炸" HUP INT TSTP
while true
do
read -p "请输入连接主机编号信息: " num
read -p "请输入账号: " user
# read -p "请输入要执行的命令: " cmd
case $num in
1)
ssh $user@192.168.15.61
[ $? -ne 0 ] && echo "connect faild"
;;
2)
ssh $user@192.168.15.41
[ $? -ne 0 ] && echo "connect faild"
;;
*)
echo "请输入连接主机信息"
esac
done
# 方式二
[root@openvpn day3]# cat jump.sh
#!/bin/bash
docter=192.168.15.101
while true
read -p "请输入账号: " user
do
ssh $user@$docter
if [ $? -eq 0 ];then
echo "connect faild"
else
echo "请输入连接主机信息"
fi
done
浙公网安备 33010602011771号