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

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

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

╭─ ~/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

#!/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.

#!/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

╭─ ~/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."

╭─ ~/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. 

#!/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

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

#!/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."

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

#!/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 $?"

#!/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

#!/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 

mynum=200

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

#!/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

#!/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

nano myscript.sh

#给脚本赋予执行的权限
sudo chmod +x myscript.sh

./myscript.sh

cat myscript.sh

ls
pwd

#!/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

.       - Any Character Except New Line 除了换行符的任意字符
\d      - Digit (0-9) 数字
\D      - Not a Digit (0-9) 非数字
\w      - Word Character (a-z, A-Z, 0-9, _) 单词字符，大小写字母+数字+下划线
\W      - Not a Word Character 非单词字符
\s      - Whitespace (space, tab, newline) 空白字符，空格+tab+换行符
\S      - Not Whitespace (space, tab, newline) 非空白字符

\b      - Word Boundary 边界字符-单词边界
\B      - Not a Word Boundary 非单词边界(没有单词边界)
^       - Beginning of a String
$       - End of a String

[]      - Matches Characters in brackets
[^ ]    - Matches Characters NOT in brackets
|       - Either Or
( )     - Group

Quantifiers:
*       - 0 or More
+       - 1 or More
?       - 0 or One
{3}     - Exact Number
{3,4}   - Range of Numbers (Minimum, Maximum)


#### Sample Regexs ####

[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+