Perhaps your difficulty is not with XPath, but rather with the command interpreter (bash?) on your system? Try surrounding your query with "single-quotes", i.e. make the command line query '/myroot/myelement[ type="a"]' and see if the result becomes more meaningful.
This was exactly the problem. Thanks to you and also to Michael Hanson off-list for pointing this out as well.
Sorry for the diversion - I should have caught my error, but I learned quite a bit from the responses anyway.
Stefan Jeglinski