[HADOOP-9267] hadoop -help, -h, --help should show usage instructions

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 3.0.0-alpha1
• Fix Version/s: 2.1.0-beta
• Target Version/s: 2.1.0-beta
• Hadoop Flags: Reviewed
• Assignee: Andrew Wang
• Reporter: Andrew Wang
• Created: 31/Jan/13 03:29
• Updated: 12/May/16 18:21
• Resolved: 22/Feb/13 18:38

Description

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:

-> % 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.

Same applies for the `hdfs` script.