How to make node outpus into log file?

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under the dir,I could see some logs like stdoutxxx.log,roslaunchxxxx.log,master.log,but I want my node`s message can also saved as mynode.log,not only in the stdout.log.

and I found that fi write the node with python,so the output will write into a log file name node_xxxx.log,but c++ not !

I'm not sure about the individual node log. But before that, to avoid an xyproblem what is the actual goal you are trying to achieve by saving this log file.