Commands and special symbols in the shell

1. Record the command:!

！！ : Continuous "! "indicates that the last instruction was executed

！ N: Represents the second instruction in the execution of the command history

Note:! 2 actually shut me down.

！ String (string greater than 1) indicates the last time the command history was executed

2. Wildcard characters

"*" matches 0 or more characters, "? "Matches one character

3. Input/Output redirection: For changing the command input and output

4. Pipe symbol "|"

The output of the previous instruction as input to the latter instruction

5. Remove the tilde "\" to revert the following special characters (such as *) to normal characters

6.grep: Full search of regular expressions and print out the lines

7.pstree: Display all the processes in the Linux system in a tree-shaped structure

8.export: Just declare this variable so that the shell's child shell knows the variable, and if the export does not add any variable names then all the variables will be declared.

9.$ as the identifier before the variable

10. If you want to run more than two or two commands in a row, you need to add a semicolon between the commands

11. "~": Indicates the user's home directory, root user's home directory is/root, ordinary user is/home/username

"&": Put a command in the background to perform the need to add

13. redirect Symbols; >,>> is the meaning of substitution and addition respectively. 2>,2>> Redirect to text

14.[] is a character combination: represents any of the character combinations

Commands and special symbols in the shell