Nohup is not writing log to output file

Question

You can run Python with the -u flag to avoid output buffering:

nohup python -u ./cmd.py > cmd.log &

It looks like you need to flush stdout periodically (e.g. sys.stdout.flush()). In my testing Python doesn't automatically do this even with print until the program exits.

• Using -u with nohup worked for me. Using -u will force the stdout, stderr streams to be unbuffered. It will not affect stdin. Everything will be saved in "nohup.out " file. Like this-

  nohup python -u your_code.py &
  

  You can also save it into your directory. This way-

  nohup python -u your_code.py > your_directory/nohup.out &
  

• Also, you can use PYTHONUNBUFFERED. If you set it to a non-empty string it will work same as the -u option. For using this run below commands before running python code.

  export PYTHONUNBUFFERED=1
  

  or

  export PYTHONUNBUFFERED=TRUE
  

P.S.- I will suggest using tools like cron-job to run things in the background and scheduled execution.

export PYTHONUNBUFFERED=1
nohup ./cmd.py > cmd.log &

or

nohup python -u ./cmd.py > cmd.log &

https://docs.python.org/2/using/cmdline.html#cmdoption-u

Python 3.3 and above has a flush argument to print and this is the only method that worked for me.

print("number to train = " + str(num_train), flush=True)
print("Using {} evaluation batches".format(num_evals), flush=True)