Special variables to refer to arguments

• $0 - Name of the script
• $1 to $9 - Arguments to the script. $1 is the first argument and so on
• $@ - All the arguments
• $# - Number of arguments
• $? - Return code of the previous command
• $$ - Process identification number (PID) for the current script
• !! - Entire last command, including arguments
• $_ - Last argument from the last command