Redirect python script output to grep

Question

There is a python script that builds cocos2dx-project. When it runs it prints out all the warning and error messages. But I want to get only those lines that contain "error". Therefore, I do the following:

python ./build_native.py | grep "error"

But it still prints everything, not only "error" lines.

EDIT:

In case you need the content of the script file, you can see it here.

Woodard

The above works perfectly fine for a script I just wrote that alternates printing "hello" and "error" 20 times. Mind giving us a sample of the output of build_native.py? – Multifoliate

See my edit please. Actually it is not the direct output of the script but the compiler that script invokes. Does this change something the way pipe works? – Woodard

Answer 1

You need to redirect stderr to stdout. Only then will grep filter out all lines not containing "error"

python ./build_native.py 2>&1 | grep "error" 

Evolve

Thanks! How could I forget? That's how bad to program in windows. :( – Woodard

Answer 2

You may want to try this, if you just want to pipe error:

python ./build_native.py 2>&1 >/dev/null | grep "error" 

Entente

This will hide stdout messages. – Multifoliate

Don't you want this? My assumption was that OP do not want to include error in stdout, only error in traceback. – Entente

I don't presume to know what the OP wants. – Multifoliate