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

• $_ last argument of last command
• $# number of arguments passed to current script
• $* / $@ list of arguments passed to script as string / delimited list

off the top of my head. Google for bash special variables.