文章目录
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
;;
*)
二、案例使用
案例1:(用户登录判断脚本)
#!/bin/bash
read -p "username: " -t 5 username
echo
if [ -z $username ];then
username="default"
fi
case $username in
root)
echo "管理员用户"
;;
egon)
echo "普通用户"
;;
default)
echo "默认用户"
;;
*)
echo "其他用户"
案例2:(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:(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
案例4:(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 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
# read -p "请输入要执行的命令: " cmd
case $num in
1)
ssh [email protected]
[ $? -ne 0 ] && echo "connect faild"
;;
2)
ssh [email protected]
[ $? -ne 0 ] && echo "connect faild"
;;
*)
echo "请输入连接主机信息"