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From Dave Shine <Dave.Sh...@channelintelligence.com>
Subject RE: [jira] [Created] (HADOOP-7325) hadoop command - do not accept class names starting with a hyphen
Date Tue, 24 May 2011 12:19:09 GMT
I'm not sure if this is the intended behavior, but it sounds like this JIRA will change it.
 I found out the hard way that running

        hadoop jar myMapReduceJob.jar

runs the M/R job with the current hadoop configuration.  However running

        hadoop -jar myMarReduceJob.jar

runs the M/R job with a different configuration, something that appears to be stand alone
mode.  It drove me nuts for a few days before I realized that sometimes I was typing the dash
and sometimes not.


-----Original Message-----
From: Brock Noland (JIRA) [mailto:jira@apache.org]
Sent: Monday, May 23, 2011 9:23 PM
To: common-dev@hadoop.apache.org
Subject: [jira] [Created] (HADOOP-7325) hadoop command - do not accept class names starting
with a hyphen

hadoop command - do not accept class names starting with a hyphen

                 Key: HADOOP-7325
                 URL: https://issues.apache.org/jira/browse/HADOOP-7325
             Project: Hadoop Common
          Issue Type: Improvement
          Components: scripts
            Reporter: Brock Noland
            Priority: Minor
         Attachments: hadoop-illegal-class-name-0.patch

If this is committed I will look at patches for hdfs and mapred.

When teaching a good portion of the students in every single class execute:

$ hadoop -fs ls /

The -fs is passed directly to the JVM and the JVM fails to start:

$ ./bin/hadoop -fs ls /
Unrecognized option: -fs
Could not create the Java virtual machine.

Which is confusing and typically requires explanation. The attached patch improves that behavior:

$ ./bin/hadoop -fs ls /
Error: No command named `-fs' was found. Perhaps you meant `hadoop fs'

The only risk I can see is if someone is abusing the implementation of hadoop command doing
something like so:

$ ./bin/hadoop -Xmx1g  org.apache.hadoop.util.RunJar
RunJar jarFile [mainClass] args...

The hadoop command does not appear to advertise allowing JVM options before the classname.

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