What is a Unix Guru?

People who come into contact with the UNIX system are often told : "If you have trouble, see so-and-so, he's a guru", or "Bob there is a real Unix hacker". Often they are baffled by these appellations, and do not pursue the matter further. What is a "Unix Hacker ?". How does he differ from a "guru" ? To answer these and other questions, here is the UNIX HIERARCHY :

beginner

insecure with the concept of a terminal
has yet to learn the basics of vi
has not figured out how to get a directory
still has trouble with typing <RETURN> after each line of input

novice

knows that ls will produce a directory
use the editor, but calls it vye.
has heard of C but never used it
has had his first bad experience with rm
is wondering how to read his mail
is wondering why the person next to him seems to like Unix so very much

user

uses vi and nroff, but inexpertly
had heard of regular-expr's but never seen one
uses egrep to search for fixed strings
has figured out that '-' precedes options
is wondering how to move a directory
has attempted to write C program and has decided to stick with pascal
thinks that sdb is a brand of stereo component
knows how to read his mail and is wondering how to read the news

knowledgeable user

uses nroff with no trouble, and is beginning to learn tbl and eqn
thinks that fgrep is fast grep
has figured out that mv will move directories
has learned that learn doesn't help
somebody has shown him how to write C programs
once used sed to do some text substitution
has seen sdb used but does not use it himself
thinks that make is only for wimps

expert

uses sed when necessary
uses macro's in vi, uses ex when necessary
posts news at every possible opportunity
writes csh scripts occasionally
writes C programs using vi and compiles with cc
has figured out what && and || are for
thinks that human history started with !h

hacker

uses sed and awk with comfort
uses undocumented features of vi
writes C code with cat > and compiles with !cc
uses adb because he doesn't trust source debuggers
can answer questions about the user environment
writes his own 'nroff' macros to supplement standard ones
writes scripts for Bourne shell (/bin/sh)

guru

uses m4 and lex with comfort
writes assembly code with cat >
uses adb on the kernel while system is loaded
customizes utilities by patching the source
reads device driver source with his breakfast
can answer any Unix question after a little thought
uses make for anything that requires two or more distinct commands to archive
has learned how to breach security, but no longer needs to try

wizard

writes device drivers with cat >
fixes bugs by patching the binaries
can answer any question before ask
writes his own troff macro packages
is on first-name basis with Dennis, Bill and Ken