Shell编程之case条件
一、case条件语句
1.语法
case "变量" in
值 1)
指令 1...
;;
值 2)
指令 2...
;;
*)
指令 3...
esac
case条件语句的执行流程逻辑图
2.实践
（1）根据用户输入判断输入的是哪个数字
[root@codis-178 ~]# cat 9_1.sh
#!/bin/bash
read -p "Please input a number:" ans
case "$ans" in
1)
echo "The num you input is 1"
;;
2)
echo "The num you input is 2"
;;
[3-9])
echo "The num you input is $ans"
;;
*)
echo "Please input [0-9] int"
exit;
esac
[root@codis-178 ~]# sh 9_1.sh
Please input a number:2
The num you input is 2
[root@codis-178 ~]# sh 9_1.sh
Please input a number:5
The num you input is 5
[root@codis-178 ~]# sh 9_1.sh
Please input a number:10
Please input [0-9] int
（2）打印一个水果菜单
1）apple
2）pear
3）banana
4）cherry
当用户输入对应的数字选择水果时，告诉他选择的水果是什么，并给水果单词加上一种颜色。
[root@codis-178 ~]# cat 9_2.sh
#!/bin/bash
RED_COLOR='\E[1;31m'
GREEN_COLOR='\E[1;32m'
YELLOW_COLOR='\E[1;33m'
BLUE_COLOR='\E[1;34m'
RES='\E[0m'
echo '
==============
1.apple
2.pear
3.banana
4.cherry
============
'
read -p "pls select a num:" num
case "$num" in
1)
echo -e "${RED_COLOR}apple${RES}"
;;
2)
echo -e "${GREEN_COLOR}pear${RES}"
;;
3)
echo -e "${YELLOW_COLOR}banana${RES}"
;;
4)
echo -e "${BLUE_COLOR}cherry${RES}"
;;
*)
echo "muse be {1|2|3|4}"
esac
[root@codis-178 ~]# sh 9_2.sh
9_2.sh: line 6: E[0m: command not found
==============
1.apple
2.pear
3.banana
4.cherry
============
pls select a num:1
apple
[root@codis-178 ~]# sh 9_2.sh
9_2.sh: line 6: E[0m: command not found
==============
1.apple
2.pear
3.banana
4.cherry
============
pls select a num:2
pear
[root@codis-178 ~]# sh 9_2.sh
9_2.sh: line 6: E[0m: command not found
==============
1.apple
2.pear
3.banana
4.cherry
============
pls select a num:3
banana
说明：
1）\E可以使用\033替代
2）[1的数字1表示加粗
3）31m表示红色
4）[0m表示关闭所有属性（[1m表示高亮度，[4m表示下划线，[5m表示闪烁）
（3）给指定内容加指定的颜色
[root@codis-178 ~]# cat 9_3.sh
#!/bin/bash
plus_color(){
RED_COLOR='\E[1;31m'
GREEN_COLOR='\E[1;32m'
YELLOW_COLOR='\E[1;33m'
BLUE_COLOR='\E[1;34m'
PINK_COLOR='\E[1;35m'
RES='\E[0m'
if [ $# -ne 2 ];then
echo "Usage:$0 content {red|yellow|blue|green|pink}"
exit
fi
case "$2" in
red|RED)
echo -e "${RED_COLOR} $1 ${RES}"
;;
yellow|YELLOW)
echo -e "${YELLOW_COLOR} $1 ${RES}"
;;
green|GREEN)
echo -e "${GREEN_COLOR} $1 ${RES}"
;;
blue|BLUE)
echo -e "${BLUE_COLOR} $1 ${RES}"
;;
pink|PINK)
echo -e "${PINK_COLOR} $1 ${RES}"
;;
*)
echo "Usage:$0 content {red|yellow|blue|green|pink}"
exit
esac
}
plus_color "I" red
plus_color "am" GREEN
plus_color "oldboy" blue
[root@codis-178 ~]# sh 9_3.sh
I
am
oldboy
3.企业应用
实现通过传参的方式往/etc/openvpn_authfile.conf里添加用户
传参要求：
参数-add，表示添加后面接的用户名
参数-del，表示删除后面接的用户名
参数-search，表示查找后面接的用户名
注：如果有同名用户，则不能添加，如果没有对应的用户，则无需删除，查找到用户或没有用户时应给出明确提示
[root@codis-178 ~]# cat 9_4.sh
#!/bin/bash
#Source function library
. /etc/init.d/functions
#config file path
FILE_PATH=/etc/openvpn_authfile.conf
[ ! -f $FILE_PATH ] && touch $FILE_PATH
usage(){
cat <<EOF
USAGE: `basename $0` {-add|-del|-search} username
EOF
}
#judge arg numbers
if [ $# -ne 2 ];then
usage
exit 2
fi
case "$1" in
-a|-add)
shift
if grep "^$1$" ${FILE_PATH} >/dev/null 2>&1
then
action $"vpnuser,$1 is exis" /bin/false
exit
else
chattr -i ${FILE_PATH}
/bin/cp ${FILE_PATH} ${FILE_PATH}.$(date +%F%T)
echo "$1" >> ${FILE_PATH}
[ $? -eq 0 ] && action $"Add $1" /bin/true
chattr +i ${FILE_PATH}
fi
;;
-d|-del)
shift
if [ `grep "\b$1\b" ${FILE_PATH}|wc -l` -lt 1 ]
then
action $"vpnuser,$1 is exis" /bin/false
exit
else
chattr -i ${FILE_PATH}
/bin/cp ${FILE_PATH} ${FILE_PATH}.$(date +%F%T)
sed -i "/^${1}$/d" ${FILE_PATH}
[ $? -eq 0 ] && action $"Del $1" /bin/true
chattr +i ${FILE_PATH}
exit
fi
;;
-s|-search)
shift
if [ `grep -w "$1" ${FILE_PATH}|wc -l` -lt 1 ]
then
echo $"vpnuser,$1 is not exist.";exit
else
echo $"vpnuser,$1 is exist.";exit
fi
;;
*)
usage
exit
;;
esac
[root@codis-178 ~]# sh 9_4.sh
USAGE: 9_4.sh {-add|-del|-search} username
[root@codis-178 ~]# sh 9_4.sh -a oldboy
Add oldboy [ OK ]
[root@codis-178 ~]# rm -f /etc/openvpn_authfile.conf
rm: cannot remove `/etc/openvpn_authfile.conf': Operation not permitted
[root@codis-178 ~]# sh 9_4.sh -search oldboy
vpnuser,oldboy is exist.
[root@codis-178 ~]# sh 9_4.sh -search oldgirl
vpnuser,oldgirl is not exist.
[root@codis-178 ~]# sh 9_4.sh -add oldgirl
Add oldgirl [ OK ]
[root@codis-178 ~]# sh 9_4.sh -s oldgirl
vpnuser,oldgirl is exist.
[root@codis-178 ~]# sh 9_4.sh -d oldgirl
Del oldgirl [ OK ]
[root@codis-178 ~]# sh 9_4.sh -s oldgirl
vpnuser,oldgirl is not exist.
说明；
1）请注意grep精准过滤的三种用法
2）shift,将$1清除，将$2替换为$1，位置参数左移（这是为了取用户名）
3）chattr 加解锁文件
开发MySQL多实例中3306实例的启动停止脚本
[root@codis-178 ~]# cat 3306.sh
#!/bin/bash
#init
port=3306
mysql_user="root"
mysql_pwd="oldboy123"
CmdPath="/usr/local/mysql/bin"
mysql_sock="/data/${port}/mysql.sock"
#startup function
function_start_mysql(){
if [ ! -e "$mysql_sock" ];then
printf "Starting MySQL...\n"
/bin/sh ${CmdPath}/mysqld_safe --default-file=/data/${port}/my.cnf 2>&1 >/dev/null &
else
printf "MySQL is running...\n"
exit
fi
}
#stop function
function_stop_mysql(){
if [ ! -e "$mysql_sock" ];then
printf "MySQL is stopped...\n"
exit
else
printf "Stoping MySQL...\n"
${CmdPath}/mysqladmin -u ${mysql_user} -p${mysql_pwd} -S /data/${port}/mysql.sock shutdown
fi
}
#restart function
function_restart_mnysql(){
printf "Restarting MySQL...\n"
function_stop_mysql
sleep 5
function_start_mysql
}
case $1 in
start)
function_start_mysql
;;
stop)
function_stop_mysql
;;
restart)
function_restart_mnysql
;;
*)
printf "Usage: /data/${port}/mysql {start|stop|restart}\n"
esac
4.case语句的适用性
（1）适合变量值较少且为固定的数字或字符串集合的情况
（2）写服务的启动脚本，传参不同且具有少量的字符串
