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https://issues.apache.org/jira/browse/HADOOP-9267?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13584510#comment-13584510
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Aaron T. Myers commented on HADOOP-9267:
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+1, I'm going to commit this momentarily.
> hadoop -help, -h, --help should show usage instructions
> -------------------------------------------------------
>
> Key: HADOOP-9267
> URL: https://issues.apache.org/jira/browse/HADOOP-9267
> Project: Hadoop Common
> Issue Type: Bug
> Affects Versions: 3.0.0
> Reporter: Andrew Wang
> Assignee: Andrew Wang
> Priority: Minor
> Attachments: hadoop-9267-1.patch, hadoop-9267-2.patch
>
>
> It's not friendly for new users when the command line scripts don't show
> usage instructions when passed the defacto Unix usage flags. Imagine this
> sequence of commands:
> {noformat}
> -> % hadoop --help
> Error: No command named `--help' was found. Perhaps you meant `hadoop -help'
> -> % hadoop -help
> Error: No command named `-help' was found. Perhaps you meant `hadoop help'
> -> % hadoop help
> Exception in thread "main" java.lang.NoClassDefFoundError: help
> Caused by: java.lang.ClassNotFoundException: help
> at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
> at java.security.AccessController.doPrivileged(Native Method)
> at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
> at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
> at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
> at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
> Could not find the main class: help. Program will exit.
> {noformat}
> Same applies for the `hdfs` script.
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