SHELL on 随记

16-18

Tue, 24 Dec 2024 09:46:52 +0800

向bash脚本添加参数#

basic#

─ ~/shellTest ly@vmmin 10:37:24
╰─❯ cat ./16myscript_cls.sh 
#!/bin/bash

echo "You entered the argument: $1,$2,$3, and $4."

结果

╭─ ~/shellTest 16s ly@vmmin 10:37:18
╰─❯ ./16myscript_cls.sh Linux1 Linux2
You entered the argument: Linux1,Linux2,, and .

示例1#

╭─ ~/shellTest ly@vmmin 10:41:45
╰─❯ cat ./16myscript_cls.sh 
#!/bin/bash

ls -lh $1

#echo "You entered the argument: $1,$2,$3, and $4."
╭─ ~/shellTest ly@vmmin 10:41:28
╰─❯ ./16myscript_cls.sh /etc
total 792K
-rw-r--r-- 1 root root 3.0K May 25 2023 adduser.conf
-rw-r--r-- 1 root root 44 Dec 17 15:26 adjtime
-rw-r--r-- 1 root root 194 Dec 23 22:38 aliases
drwxr-xr-x 2 root root 4.0K Dec 23 22:38 alternatives
drwxr-xr-x 2 root root 4.0K Dec 17 15:24 apparmor
drwxr-xr-x 8 root root 4.0K Dec 17 15:25 apparmor.d
drwxr-xr-x 9 root root 4.0K Dec 17 15:30 apt
-rw-r----- 1 root daemon 144 Oct 16 2022 at.deny
-rw-r--r-- 1 root root 2.0K Mar 30 2024 bash.bashrc

示例2#

#!/bin/bash

lines=$(ls -lh $1 | wc -l) #行计数

echo "You hava $(($lines-1)) objects in the $1 directory."
#$(($lines-1))这里用到了子shell

#echo "You entered the argument: $1,$2,$3, and $4."

╭─ ~/shellTest ly@vmmin 10:48:06
╰─❯ ls -lh logfiles 
total 12K
-rw-r--r-- 1 ly ly 0 Dec 22 23:07 a.log
-rw-r--r-- 1 ly ly 120 Dec 22 23:17 a.log.tar.gz
-rw-r--r-- 1 ly ly 0 Dec 22 23:07 b.log
-rw-r--r-- 1 ly ly 121 Dec 22 23:17 b.log.tar.gz
-rw-r--r-- 1 ly ly 0 Dec 22 23:07 c.log
-rw-r--r-- 1 ly ly 121 Dec 22 23:17 c.log.tar.gz
-rw-r--r-- 1 ly ly 0 Dec 22 23:15 xx.txt
-rw-r--r-- 1 ly ly 0 Dec 22 23:15 y.txt
╭─ ~/shellTest ly@vmmin 10:48:10
╰─❯ ./16myscript_cls.sh logfiles
You hava 8 objects in the logfiles directory.

head，表示前十行，可以看出total这些被算作一行了，所以上面的shell中-1

12-15

Mon, 23 Dec 2024 21:03:03 +0800

functions 函数#

以update这个脚本为基础编改
作用

减少重复代码

#!/bin/bash

release_file=/etc/os-release
logfile=/var/log/updater.log
errorlog=/var/log/updater_errors.log

check_exit_status(){
 if [ $? -ne 0 ]
 then
 echo "An error occured,please check the $errorlog file."
 fi
}

if grep -q "Arch" $release_file 
then
 sudo pacman -Syu 1>>$logfile 2>>$errorlog
 check_exit_status
fi

if grep -q "Ubuntu" $release_file || grep -q "Debian" $release_file 
then
 sudo apt update 1>>$logfile 2>>$errorlog
 check_exit_status
 #默认yes
 sudo apt dist-upgrade -y 1>>$logfile 2>>$errorlog
 check_exit_status
fi

CaseStatements#

脚本#

╭─ ~/shellTest ly@vmmin 22:32:52
╰─❯ cat ./13myscript_cls.sh 
#!/bin/bash

finished=0

while [ $finished -ne 1 ]
do
 echo "What is your favorite Linux distribution?"
 
 echo "1 - Arch"
 echo "2 - CentOS"
 echo "3 - Debian"
 echo "4 - Mint"
 echo "5 - Something else.."
 echo "6 - exit"
 
 read distro;
 case $distro in 
 1) echo "Arch is xxx";;
 2) echo "CentOS is xbxxx";;
 3) echo "Debian is bbbxx";;
 4) echo "Mint is xxxxsss";;
 5) echo "Something els.xxxxx";;
 6) finished=1
 echo "now will exit"
 ;;
 *) echo "you didn't enter an xxxx choice."
 esac
done

echo "Thanks for using this script."

脚本执行#

╭─ ~/shellTest ly@vmmin 22:32:11
╰─❯ ./13myscript_cls.sh 
What is your favorite Linux distribution?
1 - Arch
2 - CentOS
3 - Debian
4 - Mint
5 - Something else..
6 - exit
3
Debian is bbbxx
What is your favorite Linux distribution?
1 - Arch
2 - CentOS
3 - Debian
4 - Mint
5 - Something else..
6 - exit
u
you didn't enter an xxxx choice.
What is your favorite Linux distribution?
1 - Arch
2 - CentOS
3 - Debian
4 - Mint
5 - Something else..
6 - exit
6
now will exit
Thanks for using this script.

ScheduleJobs#

作用#

脚本在特定时间运行

07-10

Sat, 21 Dec 2024 12:00:26 +0800

WhileLoops#

范例#

#!/bin/bash

myvar=1
#小于或者等于10
while [ $myvar -le 10 ]
do
 echo $myvar
 myvar=$(( $myvar + 1 ))
 sleep 0.5
done

运行

╭─ ~/shellTest ≡ ly@vmmin 12:10:33
╰─❯ ./71myscript_cls.sh 
1
2
3
4
5
6
7
8
9
10

数字会每隔0.5s就输出一次
对于myvar=$(( $myvar + 1 )) ，$((expression))形式表示算数运算，而且其中的空格是可以省略的

范例2#

#!/bin/bash

while [ -f ~/testfile ]
do
 echo "As of $(date),the test file exists."
 sleep 5
done

echo "As of $(date), the test ....has gone missing."

用来测试文件是否存在，运行前先新建一下文件touch ~/testfile 运行一会后把文件删除，如图

06ExitCode

Sat, 21 Dec 2024 10:25:30 +0800

意义#

用来确定代码是否执行成功

例子#

ls -l /misc
echo $? #输出2
ls -l ~
echo $? #输出0

$?用来显示最近一个命令的状态，零表示成功，非零表示失败

#!/bin/bash
#这个例子之前，作者用 sudo apt remove htop 命令把htop删除了
package=htop
sudo apt install $package

echo "The exit code for ....is $?"

安装完毕后显示返回0

另一个示例

#!/bin/bash

package=notexist
sudo apt install $package

echo "The exit code for ....is $?"
#执行后显示
#Reading package lists... Done
#Building dependency tree... Done
#Reading state information... Done
#E: Unable to locate package notexist
#The exit code for ....is 100

配合if语句#

基本功能#

#!/bin/bash

package=htop
sudo apt install $package

if [ $? -eq 0 ]
then
 echo "The installation of $package success..."
 echo "new comman here:"
 which $package
else
 echo "$package failed ..."
fi

之前前作者用sudo apt remove htop又把htop删除了，不过其实不删除也是走的 echo "The installation of ....."这个分支
结果：

05If

Fri, 20 Dec 2024 18:03:12 +0000

在shell中，零为真，非零为假。

if then fi#

mynum=200

#[和]前后都要有空格
if [ $mynum -eq 200 ]
then
 echo "The condition is true."
fi

编辑之后，按ctrl + O 保存文件
ctrl + T + Z 保持在后台，fg+回车恢复

#!/bin/bash

mynum=200

#[和]前后都要有空格
if [ $mynum -eq 200 ]
then
 echo "The condition is true."
fi

if [ $mynum -eq 300 ]
then
 echo "The variable does not equal 200."
fi

else if#

#!/bin/bash

mynum=300

#[和]前后都要有空格
if [ $mynum -eq 200 ]
then
 echo "The condition is true."
else
 echo "The variable does not equal>
fi

01-04

Fri, 20 Dec 2024 15:28:33 +0000

意义#

执行一系列命令

视频框架#

介绍，欢迎
HelloWorld
变量
数学函数
if语句
退出代码
while循环
更新脚本，保持服务器最新状态
for循环
脚本应该存储在文件系统哪个位置
数据流，标准输入、标准输出、标准错误输出
函数
case语句
调度作业（SchedulingJobs）Part1
调度作业（SchedulingJobs）Part2
传递参数
备份脚本

准备#

需要一台运行Linux系统的计算机（或虚拟机）

一些基本操作#

新建或编辑脚本#

nano myscript.sh

内容#

ctrl + o 保存，ctrl + x 退出

如何执行脚本#

权限#

#给脚本赋予执行的权限
sudo chmod +x myscript.sh

执行#

执行前查看权限#

运行#

./myscript.sh

查看脚本#

cat myscript.sh

shebang#

告诉系统哪个解释器准备运行脚本(不特别指定的情况)，比如bash ./myscript.sh就特别指明了用bash运行脚本，所以这里指的是./myscript.sh这种情况使用的哪个默认解释器

#!/bin/bash

echo "Hello World!"

echo "My current working directory is:"
#结果中pwd会另取一行跟这里的显式换行没关系， 我猜是echo在最末尾加了\n换行符




pwd