第13章 学习shell script

由于博客园中dollar符号有别的意义，所以文中的dollar符号使用￥表示

第一个script

[root@localhost script]# cat -n sh01.sh
         #!/bin/bash
         #Program:
         #This program shows "Hello World!" in your screen.
         PATH=/usr/local/java/jdk1..0_91/bin:/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin:/root/bin:~/bin
         export PATH;
         echo -e "Hello World! \a \n"
         exit 

第一行：#！/bin/bash 声明这个script使用的shell名称

第二三行：注释

第四行：环境变量的声明，这样程序执行时可以直接执行一些外部命令，而不必写绝对路径

第五行：使环境变量生效

第六行：主程序部分

第七行：使用exit命令让程序中断，并且传回一个数值给系统，执行完该script后，使用echo ￥?可以得到该值。

[root@localhost script]# vi sh01.sh
[root@localhost script]# ./sh01.sh
Hello World!  

//查看上面script返回给系统的值
[root@localhost script]# echo ￥?

简单的shell script练习

交互式脚本：变量内容由用户确定

[root@localhost script]# cat -n sh02.sh
         #!/bin/bash
         PATH=/usr/local/java/jdk1..0_91/bin:/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin:/root/bin:~/bin
         export PATH

         read -p "please input your first name:" firstname #tell user to input their name
         read -p "please input your last name:" lastname
         echo -e "\n Your full name is:$firstname $lastname"
[root@localhost script]# sh sh02.sh
please input your first name:wu
please input your last name:chao

 Your full name is:wu chao
[root@localhost script]# 

随日期变化：利用日期创建文件

//查看script脚本
[root@localhost script]# cat sh03.sh
#!/bin/bash
PATH=/usr/local/java/jdk1..0_91/bin:/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin:/root/bin:~/bin
export PATH

echo -e "I will use 'touch' command to create 3 files."
read -p "please input your file name:" fileuser

filename=￥{fileuser:-"filename"}
date1=￥(date -d -2day +%Y%m%d)
date2=￥(date -d -1day +%Y%m%d)
date3=￥(date +%Y%m%d)

file1=￥{filename}￥{date1}
file2=￥{filename}￥{date2}
file3=￥{filename}￥{date3}

touch "￥file1"
touch "￥file2"
touch "￥file3"

//执行该脚本
[root@localhost script]# sh sh03.sh
I will use 'touch' command to create  files.
please input your file name:testFile
[root@localhost script]# 

//查看结果
[root@localhost script]# ls -l testFile*
-rw-r--r--.  root root  7月   : testFile20160717
-rw-r--r--.  root root  7月   : testFile20160718
-rw-r--r--.  root root  7月   : testFile20160719
[root@localhost script]# 

注：￥()是执行里面的代码得到的结果。￥{}取变量的值。

数值运算

[root@localhost script]# cat sh04.sh
#!/bin/bash
PATH=/usr/local/java/jdk1..0_91/bin:/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin:/root/bin:~/bin
export PATH

echo -e "please input two numbers:"
read -p "first number:" n1
read -p "second number:" n2

total=￥((￥n1*￥n2))
echo -e "\n The result of ￥n1 * ￥n2 is ==> ￥total"
[root@localhost script]#
[root@localhost script]# sh sh04.sh
please input two numbers:
first number:
second number:

 The result of  *  is ==>
[root@localhost script]# 

var=￥((运算内容))

用于计算

[root@localhost script]# echo ￥((*))

script的执行方式区别（source，sh script，./script）

利用直接执行的方式执行script

比如使用“sh sh01.sh”来执行脚本时，该脚本会使用一个新的bash环境（子进程）。即脚本实在子进程的bash环境执行的，当执行完后，子进程的变量不会传给父进程。

//查看script脚本中定义了firstname变量
[root@localhost script]# cat sh02.sh
#!/bin/bash
PATH=/usr/local/java/jdk1..0_91/bin:/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin:/root/bin:~/bin
export PATH

read -p "please input your first name:" firstname #tell user to input their name
read -p "please input your last name:" lastname
echo -e "\n Your full name is:$firstname $lastname"

//直接执行该脚本
[root@localhost script]# sh sh02.sh
please input your first name:wu
please input your last name:chao

 Your full name is:wu chao

//执行完上面的脚本后，在父进程尝试获取该变量，发现获取不到
[root@localhost script]# echo ￥firstname

[root@localhost script]# 

利用source执行脚本（父进程中执行）

//查看脚本，含有firstname变量
[root@localhost script]# cat sh02.sh
#!/bin/bash
PATH=/usr/local/java/jdk1..0_91/bin:/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin:/root/bin:~/bin
export PATH

read -p "please input your first name:" firstname #tell user to input their name
read -p "please input your last name:" lastname
echo -e "\n Your full name is:￥firstname ￥lastname"

//source方法执行脚本
[root@localhost script]# source sh02.sh
please input your first name:wu
please input your last name:chao

 Your full name is:wu chao

//父进程可以查看到该变量
[root@localhost script]# echo ￥firstname
wu
[root@localhost script]# 

善用判断式

利用test命令的测试功能

判断文件是否存在

[root@localhost script]# test -e file1 && echo "exist" || echo "not exsit"
not exsit
[root@localhost script]# test -e sh01.sh && echo "exist" || echo "not exsit"
exist
[root@localhost script]# 

常用的测试标注如下表：

文件类型判断

test -e filename

测试标志	代表意义
-e	该文件名是否存在
-f	该文件名是否存在且为文件
-d	该文件名是否存在且为目录
-b	该文件名是否存在且为block device设备
-c	该文件名是否存在且为character device设备
-S	该文件名是否存在且为一个Socket设备
-p	该文件名是否存在且为一个FIFO设备
-L	该文件名是否存在且为一个连接文件

文件权限检测

test -r filename

测试标志	代表意义
-r	检测该文件名是否存在且有可读的权限
-w	检测该文件名是否存在且有可写的权限
-x	检测该文件名是否存在且有可执行的权限
-u	检测该文件名是否存在且有SUID的权限
-g	检测该文件名是否存在且有SGID的权限
-k	检测该文件名是否存在且有Sticky bit的权限
-s	检测该文件名是否存在且为非空白文件

两个文件之间的比较

test file1 -nt file2

测试标志	代表意义
-nt	file1是否比file2新
-ot	file1是否比file2旧
-ef	file1和file2是否为同一个文件，即是否指向同一个inode

两个整数直接的判定

test n1 -eq n2

测试标志	代表意义
-eq	两数值相等
-ne	两数值不相等
-gt	n1>n2
-lt	n1<n2
-ge	n1>=n2
-le	n1<=n2

判断字符串数据

测试标志	代表意义
test -z string	判断是否为空字符串，空为true
test -n string	判断字符串是否为非空，空为false
test str1=str2	判断字符串是否相等
test str1！=str2	判断字符串是否不相等

多重条件判定

测试标志	代表意义
-a	两个条件同时成立，如test -r file -a -x file表示file同时具有r与x权限
-o	任意一个条件成立
！	反向状态，如test ！ -x file。当file不具有x权限时返回true

实例：

[root@localhost script]# cat sh05.sh
#!/bin/bash
PATH=/usr/local/java/jdk1..0_91/bin:/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin:/root/bin:~/bin
export PATH

echo -e "please input a filename,i will check the file's type and permision.\n\n"
read -p "input a filename:" filename
test -z ￥filename && echo "you must input a filename" && exit 

test ! -e ￥filename && echo "￥filename is not exsit!" && exit
test -f ￥filename && filetype="regulare file"
test -d ￥filename && filetype="directory"
test -r ￥filename && perm="readable"
test -w ￥filename && perm="￥perm writable"
test -x ￥filename && perm="￥perm executable"

echo "the filename:￥filename is a ￥filetype"
echo "and the permissions are: ￥perm"
[root@localhost script]# sh sh05.sh
please input a filename,i will check the file's type and permision.

input a filename:sh02.sh
the filename:sh02.sh is a regulare file
and the permissions are: readable writable
[root@localhost script]# 

利用判断符号[ ]

[ -z "￥HOME" ] ; echo ￥?

注意中括号两端都有空格符。

当变量比较时，如下：

@localhost script]# s1="hello world"
[root@localhost script]# [ "￥s1" == "hello" ]

而不可以使用[ ￥s1 == "hello"]

实例：

[root@localhost script]# cat sh06.sh
#!/bin/bash
PATH=/usr/local/java/jdk1..0_91/bin:/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin:/root/bin:~/bin
export PATH

echo -e "please input a filename,i will check the file's type and permision.\n\n"
read -p "please input (Y/N):" yn
[ "￥yn" == "Y" -o "￥yn" == "y" ] && echo "OK,continue" && exit
[ "￥yn" == "N" -o "￥yn" == "n" ] && echo "On,interrupt" && exit
echo "I do not know your choice " && exit
[root@localhost script]# sh sh06.sh
please input a filename,i will check the file's type and permision.

please input (Y/N):y
OK,continue
[root@localhost script]# 

shell script的默认变量(￥0,￥1...)

脚本执行时，后面可以跟多个参数，如下：

sh scriptname.sh opt1 opt2 ...

则￥0表示执行的文件名，￥1表示第一个参数……

￥#：代表参数个数

￥@：代表"￥1","￥2","￥3","￥4"之意，每个变量独立

￥*：代表"￥1c￥2c￥3c￥4"，c为分隔符，默认为空格

[root@localhost script]# cat sh07.sh
#!/bin/bash
PATH=/usr/local/java/jdk1..0_91/bin:/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin:/root/bin:~/bin
export PATH

echo -e "The script name is ==> ￥0"
echo -e "Total parameter number is ==> ￥#"

[ "￥#" -lt  ] && echo "The number of parameter is less than 2.Stop here." && exit
echo "Your whole parameter is ==> '￥@'"
echo "The 1st parameter is ==> ￥1"

[root@localhost script]# sh sh07.sh one two three four
The script name is ==> sh07.sh
Total parameter number is ==>
Your whole parameter is ==> 'one two three four'
The 1st parameter is ==> one
[root@localhost script]# 

条件判断式

利用if……then

if [ 条件判断式1 ]; then

　　执行操作

elif [ 条件判断式2 ]； then

　　执行操作

else

　　执行操作

fi

利用case...esac判断

当一个变量存在多个既定变量内容时，可以使用该语句针对不同的语句内容执行相应的操作。

case ￥变量名 in
    “第一个变量内容”）
     程序段
    ；；
    “第二个变量内容”）
    程序段
    ；；
    *）  #表示所有其他值得情况
    程序段
esac

　　　　举例：

[root@localhost script]# cat sh08.sh
#!/bin/bash
PATH=/usr/local/java/jdk1..0_91/bin:/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin:/root/bin:~/bin
export PATH

case ￥ in
    "hello")
    echo "hello,how are you?"
    ;;
    "")
    echo "you must input parameters, ex>{￥0 someword}"
    ;;
    *)
    echo "Usage ￥0 {hello}"
    ;;
esac

[root@localhost script]# sh sh08.sh wuchao
Usage sh08.sh {hello}
[root@localhost script]# sh sh08.sh hello
hello,how are you?
[root@localhost script]# 

利用function功能

function的设置一定要在程序的前面

[root@localhost script]# cat sh08.sh
#!/bin/bash
PATH=/usr/local/java/jdk1..0_91/bin:/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin:/root/bin:~/bin
export PATH

function printit(){
    echo -n "Your choice is "
}

case ￥ in
    "one")
        printit;echo ￥ | tr 'a-z' 'A-Z'
    ;;
    "two")
        printit;echo ￥ | tr 'a-z' 'A-Z'
    ;;
    *)
    echo "Usage ￥0 {one|two|three}"
    ;;
esac

[root@localhost script]# sh sh08.sh one
Your choice is ONE
[root@localhost script]# 

循环(loop)

while do done, until do done

while [ condition ]

do

　　程序段落

done

或

until [ condition ]

do

　　程序段落

done

for...do...done

for var in con1 con2 con3...
do
    程序段落
done

示例1：循环遍历多个字符串

[root@localhost script]# cat sh08.sh
#!/bin/bash
PATH=/usr/local/java/jdk1..0_91/bin:/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin:/root/bin:~/bin
export PATH

function printit(){
    echo -n "Your choice is "
}

for animal in dog cat tiger
do
    printit;echo "￥{animal}"
done

[root@localhost script]# sh sh08.sh
Your choice is dog
Your choice is cat
Your choice is tiger
[root@localhost script]# 

示例2：显示/etc/passwd的用户名和id信息

[root@localhost script]# cat sh08.sh
#!/bin/bash
PATH=/usr/local/java/jdk1..0_91/bin:/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin:/root/bin:~/bin
export PATH

function printit(){
    echo -n "Your choice is "
}
users=￥(cut -d ':' -f1 /etc/passwd)
for username in ￥users
do
    echo -n "id of user is : ";id ￥username    #id指令用于获取用户的id信息
    echo -e "username is :￥{username} \n"
done

[root@localhost script]# sh sh08.sh
id of user is : uid=(root) gid=(root) 组=(root)
username is :root 

id of user is : uid=(bin) gid=(bin) 组=(bin)
username is :bin 

id of user is : uid=(daemon) gid=(daemon) 组=(daemon)
username is :daemon 

id of user is : uid=(adm) gid=(adm) 组=(adm)
username is :adm 

id of user is : uid=(lp) gid=(lp) 组=(lp)
username is :lp 

id of user is : uid=(sync) gid=(root) 组=(root)
username is :sync 

示例3：遍历数值序列

[root@localhost script]# cat sh09.sh
#!/bin/bash
PATH=/usr/local/java/jdk1..0_91/bin:/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin:/root/bin:~/bin
export PATH

function printit(){
    echo -n "Your choice is "
}

network="192.168.247.129"
for sitenu in ￥(seq  )
do
    ping -c  -w  ￥{network}.￥{sitenu} &> /dev/null && result= || result=

    if [ "￥result"== ];then
        echo "Server ￥{network}.￥{sitenu} is UP."
    else
        echo "Server ￥{network}.￥{sitenu} is DOWN."
    fi
done

[root@localhost script]# sh sh09.sh
Server 192.168.247.129. is UP.
Server 192.168.247.129. is UP.
Server 192.168.247.129. is UP.
Server 192.168.247.129. is UP.
Server 192.168.247.129. is UP.
Server 192.168.247.129. is UP.
Server 192.168.247.129. is UP.
Server 192.168.247.129. is UP.
Server 192.168.247.129. is UP.

for...do...done的数值处理

for ((初始值；限制值；执行步长))
do
    程序段
done

示例

[root@localhost script]# cat sh10.sh
#!/bin/bash
PATH=/usr/local/java/jdk1..0_91/bin:/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin:/root/bin:~/bin
export PATH

function printit(){
    echo -n "Your choice is "
}

read -p "please input a number,I will count for 1+2+2+...+yourinput:" nu

s=
for ((i=;i<=￥nu;i=i+))
do
    s=￥((￥s+￥i))
done

echo "The result of 1+2+3+...+￥nu is ==> ￥s"
[root@localhost script]# sh sh10.sh
please input a number,I will count for +++...+yourinput:
The result of +++...+ is ==>
[root@localhost script]# 

shell script的追踪与调试

sh [-nvx] script.sh

参数：

-n：不执行script，仅查询语法问题

-v：在执行script前，先将script的内容输出到屏幕

-x：将使用到的script输出到屏幕