trying to run a script in the background redirect the output to a file
 

I wrote a short script that sleeps for 30 seconds then outputs "Done" to the screen:

sleep 30
echo Done

now I want to re-direct the output to a file, I tried:

./scriptName& > fileName

Didn't work, "Done" still came out to the screen.

Try

tried it but couldn't do any thing else until it finished, I just want it running in the background so I can do other work.

P.S. I am very new to LINUX

You have the redirection after the request to put the process in the background. Try
The "2>&1" will redirect errors as well as normal output.

need to tell it where to put stdout first then re-direct stderr to stdout

Good catch. I fixed it in my post.

When i run a python script in the background and redirect the result to a file the output is coming only few minutes
 

The redirection the result of a background python script to the file,the redirection of output is not happening after few lines.
I'm running a python script in linux ubuntu os:
python3 /pathtoscript/script.py > file.txt 2>&1 &

This thread is over nine years old -- and your question is not the same issue. You should have opened a new thread with your new and different question. You can use the report button to request the mods to split this off to a new thread.

That said, your redirection looks right. What do you mean by "not happening?"
What happens if you run the script in the foreground with no redirection? Do you get more lines than you do in the file?