DBA需要掌握的shell知识

2022-05-06 14:18:40 浏览数 (1)

每个中高级DBA都需要掌握一些简单脚本的编写，这样才能从繁杂重复的基础维护工作中解脱出来，才能有时间去研究更有价值的技术。VBird在讲shell script的时候，给出了几个经典的小范例练习，对于初学shell的人来说是很好的入门，现就根据VBird给出的几个典型练习进行近一步的系统整理，总结出bash shell的系统知识，希望能给各位读者起到抛砖引玉的作用。

  1. 顺序执行
  2. 分支判断
  3. 循环结构
  4. 巩固练习

1.顺序执行

**练习1：用户选择输入Y/N，不区分大小写，根据用户输入屏幕打印不同内容。** 考查：read，[]，exit 0，&&，echo

代码语言：javascript复制
#!/bin/bash
#Usage: user input a charector, program shows the different result.
#Author: Alfred Zhao
#Creation: 2015-05-06
#Version: 1.0.0

#1.Input 'Y' or 'N'
read -p "Input (Y/N)" input 
[ "$input" == "Y" -o "$input" == "y" ] && echo -e "you choice is: $inputn" && exit 0
[ "$input" == "N" -o "$input" == "n" ] && echo -e "you choice is: $inputn" && exit 0
echo -e "I don't know what your choice is" && exit 0

2.分支判断

两种常用的分支判断：if...else...fi分支判断，case...esac分支判断。

练习2：将练习1中的代码改写为if分支判断，使程序的执行逻辑更直观。 考查：==，|| if[]; then ... elif[]; then ... else ... fi

代码语言：javascript复制
#!/bin/bash
#Usage: user input a charector, program shows the different result.
#Author: Alfred Zhao
#Creation: 2015-05-06
#Version: 1.0.1

#1.Input 'Y' or 'N'
read -p "Input (y/n)" input
if [ "$input" == "Y" ] || [ "$input" == "y" ]; then
	echo -e "you choice is: $inputn"
	exit 0
elif [ "$input" == "N" ] || [ "$input" == "n" ]; then
	echo -e "you choice is: $inputn"
	exit 0
else
	echo -e "I don't know what you choice is.n"
	exit 0
fi

练习3：用分支判断来辨别参数1的输入是否合法。 考查：0，1

代码语言：javascript复制
#!/bin/bash
#Usage: To judge $1's identity. Aha, Only Alfred is ok. 
#Author: Alfred Zhao
#Creation: 2015-05-07
#Version: 1.0.0

if [ "$1" == "Alfred" ]; then
	echo -e "Authorization Successful! n"
	exit 0
elif [ "$1" == "" ]; then
	echo -e "Waring: Authorization is null! ex> {$0 Username}n"
	exit 0
else
	echo -e "Waring: Only Alfred can be authorized. ex> {$0 Alfred}n"
	exit 0
fi

练习4：用case判断改写练习3. 考查：case...esac判断

代码语言：javascript复制
#!/bin/bash
#Usage: To judge $1's identity. Aha, Only Alfred is ok. 
#Author: Alfred Zhao
#Creation: 2015-05-07
#Version: 1.0.1

case "$1" in
	"Alfred")
		echo -e "Authorization Successful! n"
		;;
	"")
		echo -e "Waring: Authorization is null! ex> {$0 Username}n"
		;;
	*)
		echo -e "Waring: Only Alfred can be authorized. ex> {$0 Alfred}n"
		;;
esac

3.循环结构

## while do done, until do done(不定循环) ## **练习5：输入名字直到输入的名字是“Alfred”为止。** 考查：while do done

代码语言：javascript复制
#!/bin/bash
#Usage: Input the name until it is "Alfred". 
#Author: Alfred Zhao
#Creation: 2015-05-07
#Version: 1.0.0

while [ "$name" != "Alfred" ]
do
        read -p "Please Input your name: " name
done
echo -e "nWelcome, My friend, Alfred.n"

而如果是使用until do done， 只需要修改while [ "

练习6：计算1 2 3 ... num的结果 考察：正则

代码语言：javascript复制
#!/bin/bash
#Usage: Calculate the result "1 2 ... num". 
#Author: Alfred Zhao
#Creation: 2015-05-07
#Version: 1.0.0

i=0 #i
s=0 #sum

echo -e "This program will help you calculate the result of '1 2 ... num'n"
read -p "Please input your num: " num

if [ "$(echo "$num"|grep '[0-9]'|grep -v '[:alpha:]')" == "" ]; then
        echo -e "Waring: Please input a number.n"
        exit 1
elif [ "$num" -lt "1" ]; then
        echo -e "Waring: Not support.n"
elif [ "$num" == "1" ]; then
        echo -e "1=1n"
        exit 0
elif [ "$num" == "2" ]; then
        echo -e "1 2=3n"
        exit 0
elif [ "$num" == "3" ]; then
        echo -e "1 2 3=6n"
        exit 0
else
        while [ "$i" != "$num" ]
        do
                i=$(($i 1))
                s=$(($s $i))
        done

        echo -e "n1 2 ... $num= $sn"
        exit 0
fi

for do done(固定循环)

for do done 第一种用法示例： 练习7：循环输出变量who的内容

代码语言：javascript复制
#!/bin/bash
#Usage: for do done 
#Author: Alfred Zhao
#Creation: 2015-05-07
#Version: 1.0.0

for who in mum dad brother sister 
do
        echo -e "This is my ${who}.n"
done

for do done 第二种用法示例： 练习8：计算1 2 .. 100的值

代码语言：javascript复制
#!/bin/bash
#Usage: 1 2 ... 100
#Author: Alfred Zhao
#Creation: 2015-05-07
#Version: 1.0.0
sum=0
for ((i=1; i<=100; i=i 1))
do
        sum=$(($sum $i))
done
    
echo -e "The result is $sum.n"

4.巩固练习

1.用分支判断哪些数据库默认端口在运行.

提示：不同数据库的默认监听端口不同 Oracle数据库判断netstat -tuln |grep ":1521 "是否有结果; Mysql数据库判断netstat -tuln |grep ":3306 "是否有结果; IEE数据库判断netstat -tuln |grep ":5029 "是否有结果; Vertica数据库判断netstat -tuln |grep ":5433 "是否有结果.

2.输入毕业日期，计算当前离毕业还有多少天。

(date --date="20160630" %s) days=

3.检查Linux系统所有用户的标识符与特殊参数

提示：cut -d ':' -f1 /etc/passwd

4.检查192.168.1.1~192.168.1.100的主机网络情况

提示：for site in $(seq 1 100)

reference

《鸟哥的Linux私房菜》

数据库 sql grep shell linux

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