pg_version and version

I need to know the version of an installation of postgres I have - I
have deleted the src directory for it, however, and therefore can't look
in there for documentation. I've looked at the man pages for postgres
and postmaster, and I can't find a --version argument, or the like. I'm
not quite sure what pg_version does, and I cannot find a man page for
it. It apparently requires and argument, but I do not know of what
kind.

Any suggestions..?

Look in your data directory. The file PG_VERSION is a text file containing
the version. Its rocket science man...james