compgen -c will list all the commands you could run.
compgen -a will list all the aliases you could run.
compgen -b will list all the built-ins you could run.
compgen -k will list all the keywords you could run.
compgen -A function will list all the functions you could run.
compgen -A function -abck will list all the above in one go.
source: http://stackoverflow.com/questions/948008/linux-command-to-list-all-available-commands-and-aliases
You can use the bash(1) built-in compgen