What are the semantics of *
at the beginning of a RE? It is documented (man 7 regex) that for basic REs it matches only *
(i.e., it turns to an ordinary character), but what happens for extended REs? By examples, it looks like it has the same semantics of '.*', but I cannot find any source for this.
prompt> echo "hello" | grep -E '*'
hello
prompt> echo "hello" | grep '*'
prompt>