[Shell command] $ #, $ *, $ n denote the meanings

Meaning $ #, $ *, $ n represent the

1, [$ 0] represents the file name of the current script;

  

 

  

2, $ n [] represents the transfer parameter values ​​to the n script (n is 1-9);

3, $ [*] represents all the parameters passed to the script (script name parameter is not included);

4, [$ @ $ *] and similar functions; 
5,] [$ # number of arguments passed to the script;

  

6, [?] $ Shows the last command exit status (0 means no error, any other value indicates an error);
7, the current script [$$] process ID number;
[!] $ 8, a background execution instruction PID (process running in the background of the last process ID number)