# bash arguments cheatsheet
$1, $2, ... -> are the positional parameters.
"$@" -> is an array-like construct of all positional parameters, {$1, $2, $3 ...}.
"$*" -> is the IFS expansion of all positional parameters, $1 $2 $3 ....
$# -> is the number of positional parameters.
$- -> current options set for the shell.
$$ -> pid of the current shell (not subshell).
$_ -> most recent parameter (or the abs path of the command to start the current shell immediately after startup).
$IFS -> is the (input) field separator.
$? -> is the most recent foreground pipeline exit status.
$! -> is the PID of the most recent background command.
$0 -> is the name of the shell or shell script.