Examples from https://halilsener.com/the-dollar-sign-in-nix/

command.sh

#!/usr/bin/env bash

echo "----- Positional Parameters -----"

echo $0
echo $1
echo $2
echo $#

echo "----- All the positional parameters -----"

IFS='-' 

echo $@
echo $*
echo "$@"
echo "$*"

echo "----- Iterate over the arguments -----"

for arg in "$@"
do
    echo $arg
done

echo "----- More $ -----"

echo "The exit status of last command (it was echo): $?"

echo "background" >/dev/null & # >/dev/null to discard its output
echo "PID of the background command: $!"

echo "The current PID: $$"