□ Positional parameter : It is parameter that is used in shell script
□ $0 : The first left string when running a script
□ $1 ~ $N : The positional parameters are stored in order
(${15} : Double digit positional parameters should be enclosed in brace)
□ $# : Number of positional parameter
□ $@ : All positional parameter. In a double quotation marks, each positional parameter is separated by each string
□ $* : All positional parameter. In a double quotation marks, the
positional parameters become single string