code: private void updateJobWithSplit(final JobConf job, InputSplit inputSplit) {
      if (inputSplit instanceof FileSplit) {
        FileSplit fileSplit = (FileSplit) inputSplit;
        job.set("map.input.file", fileSplit.getPath().toString());
        job.setLong("map.input.start", fileSplit.getStart());
        job.setLong("map.input.length", fileSplit.getLength());
      }
      LOG.info("split: " + inputSplit.toString());
    }
docs: Update the job with details about the file split
  @param job the job configuration to update
  @param inputSplit the file split