Linux study notes (8) -- File management (Part 2)

This article takes CentOS7this as an example.

Directory structure of this article

echo command

1 purpose

Output content to the console.

2 Basic grammar

2.1 Basic format

echo [选项] [输出内容]

2.2 Example

• Output environment variablesHOSTNAME

echo $HOSTNAME

• Output text contentHello world

echo "Hello world "

head command

1 purpose

Displays the beginning of the file. By default, the first 10 lines of the file are displayed .

2 Basic grammar

2.1 Basic format

head [选项] [文件路径]

2.2 Common options

• -n 行数NView the content of N lines in the file header. N can be any number of lines.

head -n N [文件路径]

2.3 Example

View /etc/profilethe first 8 lines of

head -n 8 /etc/profile

tail command

1 purpose

Displays the tail content of the file. By default, the last 10 lines of the file are displayed .

2 Basic grammar

2.1 Basic format

tail [选项] [文件路径]

2.2 Common options

• -n 行数N: View the content of N lines in the file header. N can be any number of lines.

tail -n N [文件路径]

• -f: Track all updates to documents in real time.

tail -f [文件路径]

2.3 Example

View /etc/profilethe last 8 lines of

tail -n 8 /etc/profile

> and >> directives

1 purpose

• >The directive represents output redirection and will overwrite the file contents .
• >>The instruction represents output append, the content is appended to the end of the file, and the file content will not be overwritten .

2 Basic grammar

2.1 Basic format

> [文件路径]

>>  [文件路径]

2.2 Example

• Write /homedirectory listing contents to file /home/info.txt(overwrite)

ls -l > /home/info.txt

• Append /homedirectory listing contents to /home/info.txtend of file

ls -l >> /home/info.txt

• Overwrite /home/test1.txtfile content with /home/test2.txtfile content

cat  /home/test1.txt > /home/test2.txt

ln command

1 purpose

• Called a soft link or symbolic link, it mainly stores links to other file paths .
• Similar to Windows shortcuts.

2 Basic grammar

2.1 Basic format

ln -s  [源文件路径] [软链接文件路径]

2.2 Example

• /homeCreate a soft link named under the directory to myrootlink to /rootthe directory

ln -s /root/ /home/myroot

• Delete the soft link /homenamed in the directory myroot(the same as removing the file)

rm /home/myroot

history command

1 purpose

• View historical commands that have been executed.
• You can also execute historical commands

2 Basic grammar

2.1 Basic format

history

2.2 Example

• Show all historical commands

history

• Show the last 5 historical instructions

history 5

• Execute historical instructions numbered 20

!20