shell: DBA需要掌握的shell知识

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

#!/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。

#!/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 

#!/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 

#!/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)

#!/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>" 

#!/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)

#!/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 

#!/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.

2.输入毕业日期，计算当前离毕业还有多少天。

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》

原文:http://www.cnblogs.com/jyzhao/p/4485553.html