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    linux基础之Shell Script入门介绍

    linux基础之Shell Script

    1 Shell Scipt
    使用指令和基本程序设计结构写成的程序,可以完成复杂的处理流程

    1.1 程序书写

    复制代码 代码如下:

    #!/bin/bash
    # Program:
    #       This program shows "Hello Wrold" in your screen.
    # History:
    # 2013/2/3 on_1y First release
    PATH=$PATH
    export PATH
    echo -e "Hello World!\a\n"
    exit 0

    第一行 #!/bin/bash 说明使用的shell类型,不同shell语法可能不同,所以要说明使用的是哪种shell
    其它#开始的表示注释,注释一般需要说明
    程序功能
    版本历史
    作者及联系方式
    设置好PATH变量,以便直接可以调用相应路径下的命令
    程序主体部分
    exit 0 表示程序执行成功,向环境返回0
    1.2 程序执行
    bash $bash sh01.sh #如果用sh sh01.sh而sh又不是指向bash,那么sh01.sh内的语法就会不一致,因为用 #sh去解释了bash语法写的shell script,针对这个程序,如果 #$type sh #得到sh is hashed (/bin/sh) #那么会输出-e Hello world!,而非Hello world!

    复制代码 代码如下:

    $./xxx.sh $chmod +x sh01.sh $./sh01.sh
    source $ source sh01.sh

    注:用bash和用source的不同在于,用bash执行时,shell script其实是在在父程序bash下新建了一个 bash子程序,这个子程序中执行,当程序执行完后,shell script里定义的变量都会随子程序的结束而消失, 而用source执行时,是在父程序bash中执行,shell script里定义的变量都还在。

    2 简单Shell练习

    2.1 例1 接收用户输入

    复制代码 代码如下:

    # !/bin/bash
    # Program:
    #       This program is used to read user's input
    # Site: www.jb51.net
    # 2013/2/3 on_1y First release
    PATH=$PATH
    export PATH
    read -p "Your first name:" firstname # tell user to input
    read -p "Your last name:" lastname # tell user to input
    echo -e "\nYour full name: $firstname $lastname"
    exit 0

    调用:

    复制代码 代码如下:

    $ bash sh02.sh
    Your first name:Minix
    Your last name:007
    Your full name: Minix 007

    2.2 例2 按日期建立相似名字的文件

    复制代码 代码如下:

    # !/bin/bash
    # Program:
    #       This program is used to create files according to date
    # History:
    # 2013/2/3 on_1y First release
    PATH=$PATH
    export PATH
    # Get filename from user
    echo -e "I will use 'touch' to create three files."
    read -p "Please input your filename:" tmpfilename
    # Prevent the user input [Enter]
    # Check whether filename exists or not
    filename=${tmpfilename:-"filename"}
    # Get the final filename according to date
    date1=$(date --date='2 days ago' +%Y%m%d) # date of 2 days ago
    date2=$(date --date='1 days ago' +%Y%m%d) # date of yesterday
    date3=$(date +%Y%m%d) # date of today
    filename1=${filename}${date1}
    filename2=${filename}${date2}
    filename3=${filename}${date3}
    # Create file
    touch "$filename1"
    touch "$filename2"
    touch "$filename3"
    exit 0

    调用:

    复制代码 代码如下:

    $ bash sh03.sh
    I will use 'touch' to create three files.
    Please input your filename:WhoKnows
    $ ls W*
    WhoKnows20130201  WhoKnows20130202  WhoKnows20130203

    3 判断式
    3.1 测试文件是否存在
    test -e filename会根据filename是否存在返回0或1,再交由echo显示结果:

    复制代码 代码如下:

    $ test -e sh01.sh  echo "Exists" || echo "Not exists"
    Exists
    $ test -e sh0x.sh  echo "Exists" || echo "Not exists"
    Not exists

    3.2 test常用选项
    3.2.1 文件类型

    复制代码 代码如下:

    -e file :file是否存在
    -f file :file是否存在且为文件
    -d file :file是否存在且为目录

    3.2.2 权限
    -r file :file是否有读的权限

    3.2.3 文件新旧比较
    -nt file1 file2 : file1 是否比 file2新

    3.2.4 整数,字符串,多重条件判断
    -z string: string是否为空
    例:输出指定文件类型及属性

    复制代码 代码如下:

    # !/bin/bash
    # Program:
    #       This program is used to output type and permission of the target file
    # History:
    # 2013/2/3 on_1y First release
    PATH=$PATH
    export PATH
    # Get filename from user
    echo -e "Input name of the file that you want to check.\n"
    read -p "Filename:" filename
    test -z $filename echo "You must input a filename." exit 0
    # Check whether the file exists or not
    test ! -e $filename echo "The file '$filename' DO NOT exists" exit 0
    # Check type and permission of the file
    test -f $filename filetype="regular file"
    test -d $filename filetype="directory"
    test -r $filename perm="readable"
    test -w $filename perm="$perm writable"
    test -x $filename perm="$perm executable"
    # Output result
    echo "The filename:$filename is a $filetype"
    echo "And Permissions are :$perm"
    exit 0

    调用:

    复制代码 代码如下:

    $ bash sh04.sh
    Input name of the file that you want to check.

    Filename:sh01.sh
    The filename:sh01.sh is a regular file
    And Permissions are :readable writable executable

    3.3 使用[]判断

    测试文件是否存在

    复制代码 代码如下:

    $ [ -e "sh01.sh" ] ; echo $?
    0
    $ [ -e "sh0x.sh" ] ; echo $?
    1

    注意[]内空格必须有
    这种方法和test的test -e "sho1.sh" ; echo $? 是一致的

    4 Shell Script 参数

    复制代码 代码如下:

    # !/bin/bash
    # Program:
    #       This program is used to ouput parameter of the shell script
    # History:
    # 2013/2/3 on_1y First release
    PATH=$PATH
    export PATH
    echo "The script's name is ==> $0"
    echo "Total parameter number is ==> $#"
    # Check whether number of the parameter is less than 2
    [ "$#" -lt 2 ] echo "The number of parameter is less than 2.Stop here." exit 0
    echo "The whole parameter is ==> '$@'"
    echo "The first parameter is ==> $1"
    echo "The first parameter is ==> $2"
    exit 0

    调用:

    复制代码 代码如下:

    $ bash sh05.sh 1a 2b 3c 4d
    The script's name is ==> sh05.sh
    Total parameter number is ==> 4
    The whole parameter is ==> '1a 2b 3c 4d'
    The first parameter is ==> 1a
    The first parameter is ==> 2b

    注:从以上程序可以看出与参数有关的预设变量如何表示

    5 条件表达式

    5.1 if 结构

    复制代码 代码如下:

    # !/bin/bash
    # Program:
    #       This program is used to show if else expression
    # History:
    # 2013/2/3 on_1y First release
    PATH=$PATH
    export PATH
    read -p "Please input [Y/N]" choice
    if [ "$choice" == "Y" ] || [ "$choice" == "y" ];then
        echo "OK, continue"
        exit 0
    fi
    if [ "$choice" == "N" ] || [ "$choice" == "n" ];then
        echo "Oh, interupt"
        exit 0
    fi
    exit 0

    调用:

    复制代码 代码如下:

    $ bash sh06.sh
    Please input [Y/N]y
    OK, continue
    $ bash sh06.sh
    Please input [Y/N]n
    Oh, interupt

    5.2 if else 结构

    复制代码 代码如下:

    # !/bin/bash
    # Program:
    #       This program is used to show if else expression
    # History:
    # 2013/2/3 on_1y First release
    PATH=$PATH
    export PATH
    read -p "Please input [Y/N]" choice
    if [ "$choice" == "Y" ] || [ "$choice" == "y" ];then
        echo "OK, continue"
        exit 0
    elif [ "$choice" == "N" ] || [ "$choice" == "n" ];then
        echo "Oh, interupt"
        exit 0
    else
        echo "Input [Y/N]"
    fi
    exit 0

    5.3 case

    复制代码 代码如下:

    # !/bin/bash
    # Program:
    #       This program is used to show case expression
    # History:
    # 2013/2/3 on_1y First release
    PATH=$PATH
    export PATH
    read -p "Tell me your choice:[1-3]=>" choice
    case $choice in
        "1")
            echo "Your choice is ONE"

        "2")
            echo "Your choice is TWO"

        "3")
            echo "Your choice is THREE"

    esac
    exit 0

    调用:

    复制代码 代码如下:

    $ bash sh08.sh
    Tell me your choice:[1-3]=>2
    Your choice is TWO
    $ bash sh08.sh
    Tell me your choice:[1-3]=>1
    Your choice is ONE
    $ bash sh08.sh
    Tell me your choice:[1-3]=>3
    Your choice is THREE

    6 函数

    复制代码 代码如下:

    # !/bin/bash
    # Program:
    #       This program is used to test function
    # History:
    # 2013/2/3 on_1y First release
    PATH=$PATH
    export PATH
    function myprint(){
        echo -n "Your choice is "
    }
    read -p "Tell me your choice:[1-3]=>" choice
    case $choice in
        "1")
            myprint;echo "ONE"

        "2")
            myprint;echo "TWO"

        "3")
            myprint;echo "THREE"

    esac
    exit 0

    调用:

    复制代码 代码如下:

    $ bash sh09.sh
    Tell me your choice:[1-3]=>1
    Your choice is ONE
    $ bash sh09.sh
    Tell me your choice:[1-3]=>2
    Your choice is TWO
    $ bash sh09.sh
    Tell me your choice:[1-3]=>3
    Your choice is THREE

    7 循环
    7.1 while

    复制代码 代码如下:

    # !/bin/bash
    # Program:
    #       This program shows while expression
    # History:
    # 2013/2/3 on_1y First release
    PATH=$PATH
    export PATH
    while [ "$choice" != "yes" ]
    do
        read -p "Give your choice [yes/no]:" choice
    done
    exit 0

    调用:

    复制代码 代码如下:

    $ bash sh10.sh
    Give your choice [yes/no]:no
    Give your choice [yes/no]:no
    Give your choice [yes/no]:nx
    Give your choice [yes/no]:yes

    7.2 for

    复制代码 代码如下:

    # !/bin/bash
    # Program:
    #       This program is used to demo for expression
    # History:
    # 2013/2/3 on_1y First release
    PATH=$PATH
    export PATH
    for choice in 1 2 3
    do
        echo "your choice is $choice"
    done
    exit 0

    调用示例:

    复制代码 代码如下:

    $ bash sh11.sh
    your choice is 1
    your choice is 2
    your choice is 3

    8 shell script的追踪与Debug
    sh -n xx.sh # 语法检查
    sh -x xx.sh # 列出xx.sh的执行过程

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