Variable of the hell script starting with $

$0 Process Execution name

$ N the nth parameter value of the process, n = 1 .. 9

$ * All parameters of a process. This option can contain more than 9 parameters.

$ # Number of Process Parameters

$ Process PID (ID of the current process running the script)

$! Run the PID of the previous background command (ID of the process of the last process running in the background)

$? The Return Value of the last command (display the exit status of the last command. 0 indicates no error. Other values indicate an error)

$-Display the current options used by shell, which have the same functions as the SET command.

[Email protected] is similar to $ *, but can be used as an array.

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Variable of the hell script starting with $