Linux Shell $ variable

The execution name of this program $n the nth parameter value of the program, n=1..9$* all parameters of the program, which can be more than 9 parameters. $# the number of parameters for this program $$ the PID of the program (the current process ID number of the script run) $! Perform the PID of the previous background instruction (process ID number of the last process running in the background) $? Executes the return value of the previous instruction (displays the exit status of the last command. 0 means no error, any other value indicates an error) $-shows the current options used by the shell, same as the set command [email protected] similar to $*, but can be used as an array

Linux Shell $ variable