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From "Zhixuan Zhu" <z...@calpont.com>
Subject Question about invoking an executable from Hadoop mapper
Date Thu, 25 Aug 2011 15:32:26 GMT
I think this should be a common use case. I'm trying to invoke an
executable from my mapper. Because my executable takes steaming input, I
used something like the following:

String lCmdStr = "hadoop dfs -cat file | myExec";

Process lChldProc = Runtime.getRuntime().exec(lCmdStr);

All executable and file names are full qualified name with path. I got
the following errors:

cat: File does not exist: |
cat: File does not exist: myExec

Looks like this kind of steaming/pipe method was not supported from a
mapper? I can take the exact command string and run it directly on a
Hadoop server and it works. Anybody have any experience with it?

I also tried to use Hadoop-steaming and it did not work either. It did
not give any error but nothing happened either. My program is supposed
to write a file on the local system and it's not there. I'm at the end
of my wit. Any help is most appreciated. Hadoop version 0.20.2.

String lCmdStr = "hadoop jar hadoop-0.20.2-streaming.jar -input
inputFile -output outputFile -mapper myExec";	    		    

Thanks very much,
Grace 
	    		

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