How do I ask "if NOT" in shell?

[Richard O'Keefe]

When you really want to write
	unless command ; then
	    stmts
	fi
you can do it by writing
	command
	if test $? != 0 ; then # command failed
	    stmts
	fi

If stmts is sufficiently simple, you can also do
	command || { stmts }