shell script 入门 笔记

shell script 入门

在 shell script 注意必须使用完全相同写在下面：

1.  指令的运行是从上而下、从左而右的分析与运行；

2.  指令的运行就如同第五章内提到的： 指令、选项不參数间的多个空白都会被忽略掉；

3.  空白行也将被忽略掉，并且 [tab] 按键所推开的空白相同规为空格键；

4.  假设读取到一个 Enter 符号 (CR) 。就尝试開始运行该行 (或该串) 命令；


5.  至亍假设一行的内容太多，则能够使用『 \[Enter] 』来延伸至下一行。

6.  『 # 』可做为批注。不论什么加在 # 后面的资料将所有被规为批注文字而被忽略。

第一个shell script。必须是hello world。哈哈

#!/bin/bash

PATH=/bin/:/sbin/:/usr/sbin/:/usr/local/sbin/:/usr/local/sbin:~/bin

export PATH
echo -e  "hello world!  \n"
exit 0
       

jasonleaster@ubuntu:~/shell_script_beginner$ sh ./sh01.sh

hello world!

特此说明一下，Ubuntu默认的shell是dash，而不是bash。echo -e时候会有问题。会把-e也打印出来。

转载link：http://webnoties.blog.163.com/blog/static/1835251412013518362635/

非常谢谢作者的blog帮我搞定了这个默认shell不是bash的问题

由于ubuntu默认的sh是连接到dash的,又由于dash跟bash的不兼容所以出错了.运行时能够把sh换成bash 文件名称.sh来运行.成功.dash是什么东西,查了一下,应该也是一种shell,貌似用户对它的诟病颇多.

by the way改动sh默认连接到bash的一种方法：

sudo dpkg-reconfigure dash

选择no就可以.

#! /bin/bash

# code writer : EOF
# code date   : 2014.07.29
# code file   : sh02.sh
# e-mail      : jasonleaster@gmail.com
# code purpose:
#               This program would ask the user to input some varible's value
#       and then print them out into the screen.

PATH=/bin/:/sbin/:/usr/sbin/:/usr/local/sbin/:/usr/local/sbin:~/bin
export PATH

read -p "Please input your first name:" first_name #give the user a message whatshould be inputed
read -p "Please input your second name" second_name
echo -e "\nYour full name is $first_name $second_name" #print out the user's name

jasonleaster@ubuntu:~/shell_script_beginner$ sh ./sh02.sh

Please input your first name:Jason

Please input your second nameLeaster



Your full name is Jason Leaster

#! /bin/bash

# code writer : EOF
# code date   : 2014.07.29
# code file   : sh04.sh
# e-mail      : jasonleaster@gmail.com
# code purpose:
#               This program was coded for demonstrating some
#       mathmatical operations on varibles which in bash script
#       If you find something wrong with my code, please touch me.
#       Thank you!

PATH=/bin/:/sbin/:/usr/sbin/:/usr/local/sbin/:/usr/local/sbin:~/bin
export PATH

echo -e "You SHOULD input 2 numbers ,I will cross them !\n"
read -p "first number: " first_num
read -p "second number: " second_num

total=$(($first_num*second_num))

echo -e "total is : $total"

jasonleaster@ubuntu:~/shell_script_beginner$ sh ./sh04.sh

You SHOULD input 2 numbers ,I will cross them !



first number: 10

second number: 25

total is : 250





不怕丢人的说，上面这地方写成$(total)差点纠结而shi。。

。

。

#! /bin/bash

# code writer : EOF
# code date   : 2014.07.29
# code file   : sh05.sh
# e-mail      : jasonleaster@gmail.com
# code purpose:
#               This program was coded for a demo for command -- test
#       If you find something wrong with my code, please touch me.
#       Thank you!

PATH=/bin/:/sbin/:/usr/sbin/:/usr/local/sbin/:/usr/local/sbin:~/bin
export PATH

echo -e "Please input a filename, I will check the filename's type and permission.\n\n"
read -p "Input a filename : " filename

test -z $filename && echo "You must input a filename." && exit 0

test ! -e $filename && echo "The filename '$filename' DO NOT exist" && exit 0

test -f $filename && filetype="regulare file"
test -d $filename && filetype="directory"
test -r $filename && perm="readable"
test -w $filename && perm="writable"
test -x $filename && perm="excutable"

echo "The filename: $filename is a $filetype"
echo "And the permissions are: $perm"

jasonleaster@ubuntu:~/shell_script_beginner$ sh ./sh05.sh

Please input a filename, I will check the filename's type and permission.





Input a filename : sh01.sh

The filename: sh01.sh is a regulare file

And the permissions are: writable

删除一个环境变量用      unset 环境变量名

#! /bin/bash

# code writer : EOF
# code date   : 2014.07.29
# code file   : sh06.sh
# e-mail      : jasonleaster@gmail.com
# code purpose:
#               This program was coded for a demo for [ A==B ]
#       If you find something wrong with my code, please touch me.
#       Thank you!

PATH=/bin/:/sbin/:/usr/sbin/:/usr/local/sbin/:/usr/local/sbin:~/bin
export PATH

read -p "Please input (Y/N) : " yn
[ "$yn" == "Y" -o "$yn" == "y" ] && echo "OK, continue" && exit 0
[ "$yn" == "N" -o "$yn" == "n" ] && echo "NO,interrupt" && exit 0
echo "I don't know what you choice is" && exit 0

jasonleaster@ubuntu:~/shell_script_beginner$ sh ./sh06.sh

Please input (Y/N) : y

OK, continue

#! /bin/bash

# code writer : EOF
# code date   : 2014.07.29
# code file   : sh07.sh
# e-mail      : jasonleaster@gmail.com
# code purpose:
#               This program was coded for a demo that user input a file name
#       and some parameters, lately program process it and print out the file
#       type and permission.
#       If you find something wrong with my code, please touch me.
#       Thank you!

PATH=/bin/:/sbin/:/usr/sbin/:/usr/local/sbin/:/usr/local/sbin:~/bin
export PATH

echo "The script name is ==> $0"
echo "Total parameter numbe is ==> $#"
[ "$#" -lt 2 ] && echo "The number of parameter is less than 2. Stop here" && exit 0
echo "Your whole parameter is ==> $@"
echo "1st parameter ==> $1"
echo "2nd parameter ==> $2"

jasonleaster@ubuntu:~/shell_script_beginner$ sh ./sh07.sh

The script name is ==> ./sh07.sh

Total parameter numbe is ==> 0

The number of parameter is less than 2. Stop here

jasonleaster@ubuntu:~/shell_script_beginner$ sh ./sh07.sh hello world

The script name is ==> ./sh07.sh

Total parameter numbe is ==> 2

Your whole parameter is ==> hello world

1st parameter ==> hello

2nd parameter ==> world

#! /bin/bash

# code writer : EOF
# code date   : 2014.07.30
# code file   : sh08.sh
# e-mail      : jasonleaster@gmail.com
# code purpose:
#               This program was coded for a demo for command -- shift
#       If you find something wrong with my code, please touch me.
#       Thank you!

PATH=/bin/:/sbin/:/usr/sbin/:/usr/local/sbin/:/usr/local/sbin:~/bin
export PATH

echo "Total parameter number is ==> $#"
echo "Your whole parameter is ==> $@"
shift
echo "Total parameter number is ==> $#"
echo "Your whole parameter is ==> $@"
shift 3
echo "Total parameter number is ==> $#"
echo "Your whole parameter is ==> $@"

jasonleaster@ubuntu:~/shell_script_beginner$ sh ./sh08.sh

Total parameter number is ==> 0

Your whole parameter is ==>

Total parameter number is ==> 0

Your whole parameter is ==>

Total parameter number is ==> 0

Your whole parameter is ==>

jasonleaster@ubuntu:~/shell_script_beginner$ sh ./sh08.sh hello world

Total parameter number is ==> 2

Your whole parameter is ==> hello world

Total parameter number is ==> 1

Your whole parameter is ==> world

Total parameter number is ==> 1

Your whole parameter is ==> world

jasonleaster@ubuntu:~/shell_script_beginner$ sh ./sh08.sh hello world jason leaster tonight

Total parameter number is ==> 5

Your whole parameter is ==> hello world jason leaster tonight

Total parameter number is ==> 4

Your whole parameter is ==> world jason leaster tonight

Total parameter number is ==> 1

Your whole parameter is ==> tonight

有意思的是假设文件名称之后没有“參数”，parameter number就是0，假设參数少于shift移动的距离(例如说代码中的shift 3),就会保留最低数目为1，假设參数少于shift移动的距离

#! /bin/bash

# code writer : EOF
# code date   : 2014.07.30
# code file   : sh08.sh
# e-mail      : jasonleaster@gmail.com
# code purpose:
#               This program was coded for a demo for "if[] ; then fi"
#       If you find something wrong with my code, please touch me.
#       Thank you!

PATH=/bin/:/sbin/:/usr/sbin/:/usr/local/sbin/:/usr/local/sbin:~/bin
export PATH

read -p "Please input (Y/N) :" yn

if [ "$yn" == "Y" -o "$yn" == "y" ]; then
        echo "OK,continue"
        exit 0
fi

if [ "$yn" == "N" -o "$yn" == "n" ]; then
        echo "Oh,interrupt!"
        exit 0
fi

echo "I don't know what your choice is" && exit 0

jasonleaster@ubuntu:~/shell_script_beginner$ sh ./sh09.sh

Please input (Y/N) :y

OK,continue

jasonleaster@ubuntu:~/shell_script_beginner$ sh ./sh09.sh

Please input (Y/N) :n

Oh,interrupt!

#! /bin/bash

# code writer : EOF
# code date   : 2014.07.30
# code file   : sh9.sh
# e-mail      : jasonleaster@gmail.com
# code purpose:
#               This program was coded for a demo for "if[] ; elif [] ;then else fi"
#       If you find something wrong with my code, please touch me.
#       Thank you!

PATH=/bin/:/sbin/:/usr/sbin/:/usr/local/sbin/:/usr/local/sbin:~/bin
export PATH

read -p "Please input (Y/N) :" yn

if [ "$yn" == "Y" -o "$yn" == "y" ]; then
        echo "OK,continue"
        exit 0
elif [ "$yn" == "N" -o "$yn" == "n" ];then
        echo "Oh,interrupt!"
        exit 0
else
        echo "Are you kidding me?

You don't know what means \"Input (Y/N)\" \n"
fi

echo "I don't know what your choice is" && exit 0

jasonleaster@ubuntu:~/shell_script_beginner$ sh ./sh10.sh

Please input (Y/N) :hehe

Are you kidding me? You don't know what means "Input (Y/N)" \n

I don't know what your choice is

#! /bin/bash

# code writer : EOF
# code date   : 2014.07.30
# code file   : sh10.sh
# e-mail      : jasonleaster@gmail.com
# code purpose:
#               This program was coded for a demo for "if[] ; elif [] ;then else fi"
#       If you find something wrong with my code, please touch me.
#       Thank you!

PATH=/bin/:/sbin/:/usr/sbin/:/usr/local/sbin/:/usr/local/sbin:~/bin
export PATH

echo "This program will print your selection !"

case $1 in
        "one")
        echo "Your choice is ONE"
        ;;
        "two")
        echo "Your choice is TWO"
        ;;
        *)
        echo "42"
        ;;
esac

jasonleaster@ubuntu:~/shell_script_beginner$ sh ./sh12.sh hello world

This program will print your selection !

42

#! /bin/bash

# code writer : EOF
# code date   : 2014.07.30
# code file   : sh13.sh
# e-mail      : jasonleaster@gmail.com
# code purpose:
#               This program was coded for a demo for "function and while loop"
#       If you find something wrong with my code, please touch me.
#       Thank you!

PATH=/bin/:/sbin/:/usr/sbin/:/usr/local/sbin/:/usr/local/sbin:~/bin
export PATH

function secret()
{
        echo "hello world!"
}

temp=10

while [  $temp != 0 ]
do
        secret
        temp=$(($temp-1))
        echo "$temp"
done

jasonleaster@ubuntu:~/shell_script_beginner$ sh ./sh13.sh

hello world!

9

hello world!

8

hello world!

7

hello world!

6

hello world!

5

hello world!

4

hello world!

3

hello world!

2

hello world!

1

hello world!

0

最后sh -x将使用do啊的script 内容显示到屏幕上，这是非常实用的參数，而-n不会显示不论什么信息

jasonleaster@ubuntu:~/shell_script_beginner$ sh -x ./sh13.sh

+ PATH=/bin/:/sbin/:/usr/sbin/:/usr/local/sbin/:/usr/local/sbin:/home/liuzjian/bin

+ export PATH

+ temp=2

+ '[' 2 '!=' 0 ']'

+ secret

+ echo 'hello world!'

hello world!

+ temp=1

+ echo 1

1

+ '[' 1 '!=' 0 ']'

+ secret

+ echo 'hello world!'

hello world!

+ temp=0

+ echo 0

0

+ '[' 0 '!=' 0 ']'

去衡山的时候，在白龙潭(应该是吧。不记得啦。。。

)遇见的两个小孩。。

。多么美好年纪啊。。。

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