What are the special dollar sign shell variables?

Question

In Bash, there appear to be several variables which hold special, consistently-meaning values. For instance,

./myprogram &; echo $!

wil

Answer 1

To help understand what do $#, $0 and $1, ..., $n do, I use this script:

#!/bin/bash

for ((i=0; i<=$#; i++)); do
  echo "parameter $i --> ${!i}"
done

Running it returns a representative output:

$ ./myparams.sh "hello" "how are you" "i am fine"
parameter 0 --> myparams.sh
parameter 1 --> hello
parameter 2 --> how are you
parameter 3 --> i am fine