SHELL

shell script get arguments

$ myscript.sh first_arg second_arg

# myscript.sh
#!/bin/bash
echo $1 # output: first_arg
echo $2 # output: second_arg

bash parameter

# 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.