arguments for script

https://superuser.com/questions/247127/what-is-and-in-linux/247131#:~:text=%22%24%40%22%20Stores%20all%20the%20arguments,first%20argument%20and%20so%20on.

$!	  gives the pid of the command (ex echo "hello" & echo $!)

$#    Stores the number of command-line arguments that 
      were passed to the shell program.
$?    Stores the exit value of the last command that was 
      executed.
$0    Stores the first word of the entered command (the 
      name of the shell program).
$*    Stores all the arguments that were entered on the
      command line ($1 $2 ...).
"$@"  Stores all the arguments that were entered
      on the command line, individually quoted ("$1" "$2" ...).
So basically, $# is a number of arguments given when your script was executed. $* is a string containing all arguments. For example, $1 is the first argument and so on. This is useful, if you want to access a specific argument in your script.

 here is a simple example. If you run following command:

./command -yes -no /home/username
$# = 3
$* = -yes -no /home/username
$@ = array: {"-yes", "-no", "/home/username"}
$0 = ./command, $1 = -yes etc.