流程控制之case语句
一、语法
case 变·量 in
模式一）
命令序列1
；；
模式二）
命令序列2
；；
...
*)
无匹配后命令序列
esac
二、案例
1）案例一
#判断用户的类型
[root@db04 /scripts/day05]# vim user.sh
#!/bin/bash
read -p "please input user name:" name
[ -z "$name" ] && echo "The user name must exist" && exit
case $name in
"root")
echo "admin"
;;
"jh")
echo "com user"
;;
*)
echo "other user"
esac
[root@db04 /scripts/day05]# chmod +x user.sh
2）案例二
#编写nginx启动脚本
[root@db04 /scripts/day05]# vim nginx.sh
#!/bin/bash
[ $# -ne 1 ] && echo "Usage: $0 {start|stop|restart|reload|status}" && exit
function start() {
ps aux |grep [n]ginx |grep -q master
if [ $? -eq 0 ];then
echo "nignx is started"
else
/usr/local/nginx/sbin/nginx &>/dev/null
if [ $? -eq 0 ];then
echo "nginx start success..."
else
echo "nginx start failed"
fi
fi
}
function stop(){
ps aux |grep [n]ginx |grep -q master
if [ $? -eq 0];then
/usr/local/nginx/sbin/nginx -s stop
sleep 3
ps aux |grep [n]ginx |grep -q master
if [ $? -ne 0 ];then
echo "nginx stop success..."
sleep 3
else
echo "nginx stop failed"
fi
else
echo "nginx is stopped"
fi
}
case $1 in
"start")
start
;;
"stop")
stop
;;
"restart")
stop
start
;;
"reload")
stop
start
;;
"status")
ps aux |grep [n]ginx |grep -q master
if [ $? -eq 0 ];then
echo "nginx is up"
else
echo "ngins is down"
fi
;;
*)
echo "Usage: $0 {start|stop|restart|reload|status}"
esac
[root@db04 /scripts/day05]# chmod +x nginx.sh
3）案列三
[root@jh shell]# vim 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@jh shell]# chmod +x nginx_stat.sh
[root@jh shell]# ./nginx_stat.sh start
start nginx [ 确定 ]
[root@jh shell]# ./nginx_stat.sh restart
restart nginx [ 确定 ]
[root@jh shell]# ./nginx_stat.sh
USAGE ./nginx_stat.sh {start|stop|restart}
4）案列四
# 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@jh shell]# action "nginx start is" :
nginx start is [ 确定 ]
[root@jh shell]# action "nginx start is" /bin/true
nginx start is [ 确定 ]
[root@jh shell]# action "nginx start is" /bin/false
nginx start is [失败]
# 代码
[root@jh shell]# vim 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 -lntup|grep ":80\b" &>/dev/null
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
5）案例五
#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@jh shell]# cat jumpserver.sh
#!/bin/bash
cat<<EOF
1. BACKUP 10.0.0.41
2. WEB02 192.168.12.21
3. WEB03 10.0.0.9
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
case $num in
1)
ssh $user@10.0.0.41
[ $? -ne 0 ] && echo "connect faild"
;;
2)
ssh $user@192.168.12.21
[ $? -ne 0 ] && echo "connect faild"
;;
*)
echo "请输入连接主机信息"
esac
done
