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From Robert Evans <ev...@yahoo-inc.com>
Subject Re: Viewing hadoop mapper output
Date Thu, 06 Oct 2011 20:41:30 GMT

Are you running in local mode?  If not you probably want to run

hadoop jar ../contrib/streaming/hadoop-0.20.2-streaming.jar -file ~/mapper.sh -mapper ./mapper.sh
-input ../foo.txt -output output

You may also want to run hadoop fs -ls output/* to see what files were produced.  If your
mappers failed for some reason then there will be no files in the output directory. And you
may want to look at the stderr logs for your processes through the web UI.

--Bobby Evans

On 10/6/11 3:30 PM, "Aishwarya Venkataraman" <avenkata@cs.ucsd.edu> wrote:

I ran the following (I am using IdentityReducer) :

./hadoop jar ../contrib/streaming/hadoop-0.20.2-streaming.jar -file
~/mapper.sh -mapper ~/mapper.sh -input ../foo.txt -output output

When I do
./hadoop dfs -cat output/* I do not see any output on screen. Is this how I
view the output of mapper ?


On Thu, Oct 6, 2011 at 12:37 PM, Robert Evans <evans@yahoo-inc.com> wrote:

> A streaming jobs stderr is logged for the task, but its stdout is what is
> sent to the reducer.  The simplest way to get it is to turn off the
> reducers, and then look at the output in HDFS.
> --Bobby Evans
> On 10/6/11 1:16 PM, "Aishwarya Venkataraman" <avenkata@cs.ucsd.edu> wrote:
> Hello,
> I want to view the mapper output for a given hadoop streaming jobs (that
> runs a shell script). However I am not able to find this in any log files.
> Where should I look for this ?
> Thanks,
> Aishwarya

Aishwarya Venkataraman
Graduate Student | Department of Computer Science
University of California, San Diego

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