[Hadoop] Example of MapReduce Program

The practical demonstration of WordCount Problem:

• To run a MapReduce Program, we need to start Hadop demons first.

• Make temp folder and file.

• Create and copy a file into HDFS. Put the file inside a separate directory. In this case, it is /input

• The MapReduce will create another directory, in this case it is /output. In that directory there will be a part file. That file will hold the final MapReduce output.

• The WordCount program is one of the default programs, that comes with Hadoop. We can use the jar file to execute the MapReduce Task.
• The syntax of using the Jar file to start MapReduce task:
  • $ hadoop jar <jar_path> <class_name> <parameters>
• In this case the parameters are the input and output directory.