There are 2 parts I am proposing in this jira. They can be fixed together in one patch.
1. Standardize help message for required parameter of $ yarn logs
YARN CLI has a command "logs" ($ yarn logs). The command always requires a parameter of "-applicationId <arg>". However, help message of the command does not make it clear. It lists -applicationId as optional parameter. If I don't set it, YARN CLI will complain this is missing. It is better to use standard required notation used in other Linux command for help message. Any user familiar to the command can understand that this parameter is needed more easily.
2. Add description for help command. As far as I know, a user cannot get logs for running job. Since I spent some time trying to get logs of running applications, it should be nice to say this in command description.