03_ common commands for files and directories

01. View Directory Contents 1.1 Terminal practical Tips 1> Auto-complete

• 文件 目录 命令 After the first few letters of the hit//, press the tab key
  • If there is no ambiguity in the input, the system will automatically complete
  • If there is another 文件 / 目录 / 命令 , press the tab key again, the system will prompt for possible commands

2> have used the command

• Press the 上 / 下 cursor key to switch back and forth between commands that have been used
• If you want to exit the selection and do not want to perform the currently selected command, you can pressctrl + c

1.2 lsCommand description

• lsis the abbreviation of the English word list , its function is to list the contents of the directory, is one of the most commonly used commands, similar to DOS dir commands

Features of files and directories under Linux

• A Linux file or directory name can have 256 a maximum of one character
• .the file to begin with is a hidden file and needs to be displayed with the-a parameter
• . Represents the current directory
• .. Represents the previous level of the directory

1.3 ls Common options

| Parameters | meaning |
| -A | Displays all subdirectories and files in the specified directory, including hidden files
| -L | Display file details in a list
| -H | Display file size in a humane way with-l

How file sizes are represented in your computer

| Units | English | meaning |
| bytes | B (Byte) | As a digital unit in a computer, typically a 8-bit binary number
| thousand | K (Kibibyte) | 1 KB = 1024x768 B, Kbytes (1024 = 2 * * 10)
| Mega | M (Mebibyte) | 1 MB = KB, Million bytes
| Gigabit | G (Gigabyte) | 1 GB = 1024x768, 1 billion bytes, gigabytes
| Too | T (Terabyte) | 1 TB = 1024x768, trillion bytes, MBytes
| Pat | P (Petabyte) | 1 PB = 1024x768 TB, petabyte bytes, Pat Byte
| Ai | E (Exabyte) | 1 EB = 1024x768 PB, exascale bytes, Ai byte
| Ze | Z (Zettabyte) | 1 ZB = EB, 10 trillion bytes, ze byte
| Yao | Y (Yottabyte) | 1 YB = 1024x768 ZB, 100 million bytes, Yao byte

Use of the 1.4 LS wildcard

| Wildcard characters | meaning |
| * | Represents an arbitrary number of characters
| ? | Represents any one character, at least 1
| [] | Indicates that any one of the character groups can be matched
| [ABC] | Match any of A, B, c
| [A-f] | Match any one of the characters from a to F range

02. Switch Directories 2.1 cd

• cdis a shorthand for the English word change directory , which is a function of changing the current working directory and is one of the most commonly used commands for users.

Note: All Linux directories and file names are case-sensitive

| Command | meaning |
| CD | Switch to the current user's home directory (/home/user directory)
| CD ~ | Switch to the current user's home directory (/home/user directory)
| Cd. | Remains unchanged in the current directory
| CD ... | Switch to Parent directory
| CD-| Can switch back and forth between the last two working directories

2.2 Relative and absolute paths

• relative path at input path, first not / or ~, relative to the directory location where the current directory is located
• Absolute path in the input path, the first is / or ~, indicating the specific directory location starting from the root/home directory

03. Create and DELETE operations 3.1 touch

• Create a file or modify a file time
  • If the file does not exist , you can create a blank file
  • If the file already exists , you can modify the last modified date of the file

3.2 mkdir

• Create a new directory

| Options | meaning |
| -P | Directory can be created recursively

the name of the new directory cannot be the same as the existing directory or file in the current directory

3.3 rm

• Delete a file or directory

Use rm the command with caution because the file cannot be recovered after deletion

| Options | meaning |
| -F | Forced deletion, ignoring nonexistent files without prompting
| -r | To delete the contents of a directory recursively, this parameter must be added when Deleting a folder

04. Copying and moving files

| Serial number | Command | Correspondence in English | function |
| 01 | Tree [directory Name] | Tree | List the file directory structure in a tree view
| 02 | CP source File Destination File | Copy | Copy files or directories
| 03 | MV Source file Destination File | Move | Move files or directories/files or directories to rename

4.1 tree

• treecommand to list the file directory structure in a tree view

| Options | meaning |
| -D | Show only Directories

4.2 cp

• cpThe function of a command is to copy the given file or directory to another file or directory , which is equivalent to a DOS copy command

| Options | meaning |
| -I. | Prompt before overwriting files
| -r | If the given source file is a directory file, the CP will recursively replicate all subdirectories and files in that directory, and the destination file must be a directory name

4.3 mv

• mvCommands can be used to move files or directories , or to rename files or directories

| Options | meaning |
| -I. | Prompt before overwriting files

05. View the contents of a file

| Serial number | Command | Correspondence in English | function |
| 01 | Cat file name | Concatenate | Ability to view file contents, create files, merge files, append file contents, and more
| 02 | More File names | more | Split-screen display of file contents
| 03 | grep search text File name | grep | Search for text file contents

5.1 cat

• catCommands can be used to view file contents , Create files , merge Files , append file contents , etc.
• catDisplays all content at once, suitable for viewing text files with less content

| Options | meaning |
| -B | Number of non-null output lines
| -N | Numbering all lines of the output

Linux also has one nl command and cat -b the effect is equivalent

5.2 more

• moreCommands can be used to display the contents of a file on a split screen, displaying only one page at a time
• Suitable for viewing text files with more content

moreoperating keys to use:

| Operation Keys | Features |
| Space Key | Show the next screen of the man page
| Enter key | One row of the scroll manual page
| B | Roll back one screen
| f | Roll forward one screen
| Q | Exit
| /word | Search Word string

5.3 grep

• Commands in Linux systems grep are a powerful text-search tool
• grepAllow the text file to pattern lookup, so-called pattern lookup, also known as regular expression, in the employment meeting detailed explanation

| Options | meaning |
| -N | Display matching lines and line numbers
| -V | Display all lines that do not contain matching text (equivalent negation)
| -I. | Ignore case

• Two common modes of finding

| Parameters | meaning |
| ^a | Beginning of line, searching for lines beginning with a
| ke$ | End of line, search for lines ending with ke

06. Other 6.1 echo 文字内容

• echoThe text specified in the parameter is displayed in the terminal and is typically used in conjunction with redirection

6.2 Redirects >And >>

• Linux allows command execution results to be redirected to a file
• Output/Append content that should be displayed on the terminal to the specified file

which

• >Represents the output, overwriting the original contents of the file
• >>Represents an append that appends content to the end of an existing file

6.3 Piping |

• Linux allows the output of one command to be piped as input to another command
• Can understand the real life of the pipe, the pipe of a plug in, the other side out, where the left and | right are divided into two ends, the end of a plug thing (write), and take something at the end (read)

Common pipeline commands are:

• more: Split screen display content
• grep: Queries the specified text based on the result of the command execution

03_ common commands for files and directories