Where is log_path file located in Ubuntu for ROS Indigo [closed]

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I have the statement <arg name="log_path" /> in a launch file which is later called in <param name="log_path" value="$(arg log_path)" />

Without any modifications to the launch file, I am getting this error in terminal arg 'log_path' is not defined. Arg xml is <arg name="log_path" value="$(arg log_path)"/> The traceback for the exception was written to the log file

One way to resolve would be to delete those lines. A better way would be to find the path to log_file as here: <arg name="log_path" default="path/to/logFile" />

Please tell me what are the ways to resolve this issue.