I think you have misunderstood.
Some(!) options to some(!) cmds have '--' versions, but not all.
There's no rule as to which.
In traditional *nix, all tool options were short, but when the GNU toolset came along (ie free toolset), they started adding long versions to make them easier to read.
In fact you may see them referred to as GNU-style options.
You just have to read the man page or eg http://linux.die.net/man/
for a given cmd to see which ones exist.
In some cases a new long option was introduced to a cmd because the obvious one-letter version was already taken, but had a different meaning to the new option.
you may want to read this and the links therein http://stackoverflow.com/questions/4...d-line-options