this-single-command-keys

this-single-command-keys is a built-in function in `C source code'.

(this-single-command-keys)

Return the key sequence that invoked this command.
More generally, it returns the last key sequence read, either by
the command loop or by `read-key-sequence'.
Unlike `this-command-keys', this function's value
does not include prefix arguments.
The value is always a vector.