Maybe my question is quite stupid , but how to become good UNIX engineer.
What to read , how to practice ?
What a good engineer must know to call himself engineer . 
Hi dude
Follow posts in this forum religiously ...Reading them only gives you a lot of knowledge in cooked form .. Go through basic unix books ...
+ Plus find a good unix box on which you can do crash and burn 
- Find a place to try unix - a server, or load cygwin (or other) to a pc
- Read this forum - learn from the examples
- Go back to step one and practice something
In all seriousness, you can begin to get good by attempting to solve forum support questions yourselves. Those that you do not understand, step through the answers yourself.
What to read... goto local bookstore and look through various unix, awk, sed, etc... books. Find one or more that match your style.
For me, I got in-depth books with lots of examples of options for unix and awk. Picked up quick guides for sed and vi (editor). But, that was "my" style of learning.
I asked because my head is all in Solaris, I am reading Solaris advanced administration and I understand what is written in that book.
I asked because I saw here is a loot of UNIX adminis, and I am trying to help if someone has a problem with Solaris, but often Jilliagre tells me what I am telling wrong 
Use, actually seriously use a UNIX machine for day to day things, don't just administer a remote box. You'll find where the holes in your knowledge are real fast when you need to do general things that weren't in the admin book. A big blank spot for a lot of folks seems to be awk, me included. I'm continually amazed at the one-line-wonders the regulars pump out while I'm still crafting a ten line bash script.
So
Lot of reading and daily UNIX usage, and The UNIX and Linux Forums - Learn UNIX and Linux from Experts of course
Yea, but not only at home.
I (and probably your next potential employer) could not respect someone calling himself UNIX Engineer without having at least 5 yrs. of working experience in a (large) company.
Ideally you will have some certification too, eg. SCSA, SCNA, SCSECA
/me is also trying to get there where you want. Gotta look for a Junior UNIX Administrator/Manager/Engineer job opportunity.
Good luck 
What about Oracle databases , shell scripting , programming in ?
Along with reading through the forums, subscribing and reading several Linux blog's regularly is also a good idea.
Imho you should know shell scripting very well, speak at least one "real" programming language fluent and have at least some basic knowledge of Oracle.
But there also many another important system related things which a UNIX engineer should know to deal with: Storage (RAID's,...), Clustering, Security,...
I think you must to read a lot of articles and books, they will give to you basic knowledge and also you need have a lot of practical works and you must have interest to work :)))
Read "The Practice of System and Network Administration" by Limoncelli and Hogan. Teaches you how to be an Admin or Engineer, not just how to do Unix. The authors were consultants with decades of real world experience in many, many datacenters. I learned more about how to be a successful professional Unix person from this book than any tech manual/textbook I ever read.
I really recommend that you try to take the official training for Solaris administration by SUN. It's very organized, and the contents of the books are really great. If you can't afford the training then get those books, and start reading and practice every topic.
Then you need a job where you face real life scenarios. This forum is very helpful, you should try the things you read here.
I was recently promoted to a jr engineer postion where the environment is about 90% Solaris.
I would say that this is my dream job accept for the fact that I haven't earned the title yet.
You have to understand that it may take years before you attain a level where you SHOULD even be considered for one of these positions. It's a combination of luck and opportunity that has gotten me this far.
I had been working in either desktop or customer support roles for the last 10years. The fact that the company I work for now was hit so hard by the recession forced many people to double and even triple the word responsibilities that they had been accustomed to. That's a good and bad thing. Good because you learn more than what your job description is.
This got me comfortable with Unix. When the opportunity arose that they needed a new unix engineer I jumped at the chance. I probably am not ready but I am hitting the books like nobody's business.
No one here can really tell you all the books you should be studying. Your companies needs are going to vary. The company I work for tends to have a very Oracle, websphere centric environment. So those are the additional skills I must have.
But there are time tested books that will really never go out of style in the foreseeable future. Unix shell programming (again based on your companies needs e.g. Korn, Bash) and Awk and sed skills. Of course the editor of your choice. I am loving the process of getting more and more comfortable of learning advanced editing with VI. But I must say I love emacs. It's actually more my style but this company is more of a vi shop. Not at a point where I want to edit my .profile on all the servers I have login's for.
The important thing is get comfortable with Unix flavor that your company uses. Then focus on the external things that will make your work more efficient. There are going to be a million ways to do the same things so tapping into and developing your own style is important.
Again I am fairly new at this so if there is anyone who needs a unix buddy, maybe we can travel this road together, just contact me and I would be more than willing to share my experiences and learn from yours.
Learn - Do - Break stuff - Fix stuff
With enough of that you should be well on the path