Bash script variables

Below is the list standard variables can be used in bash script.

• $$ = Expands to the process ID of the shell
• $0 = Name of bash script file.
• $# = Number of arguments passed to bash script 
• $1 = Argument 1
• $2 = Argument 2
• $@ = expands to the positional parameters, starting from one. i.e. "$@" is equivalent to "$1" "$2" …
• $? = Exit status of mostly recently run process