Meaning of specific compliance variables in shell scripts

$# the number of arguments passed to the script

$* displays all parameters passed to the script in a single string. Unlike positional variables, this option parameter can be more than 9

$$ the current process PID number for the script to run

$! Process number of the last process running in the background

[Email protected] is the same as $*, but uses double quotes and returns each parameter with double quotes

$-shows the current options used by the shell, same as the SET command function

$_ last parameter of previous command

$? Displays the exit status of the last command, 0 indicates successful execution, and other values are problematic

$ A script name

$n positional parameter value, n indicates position

Meaning of specific compliance variables in shell scripts