非常希望能在hadoop上做c++程序。自己对c++还是有点情节的，依据《hadoop权威指南中文第二版》Hadoop的Pipes进行了试验，并測试成功

#include <algorithm>

#include <limits.h>

#include <stdint.h>

#include <string>  

#include "Pipes.hh"

#include "TemplateFactory.hh"

#include "StringUtils.hh"  

class MaxTemperatureMapper : public HadoopPipes::Mapper {

public:

  MaxTemperatureMapper(HadoopPipes::TaskContext& context) {

  }

  void map(HadoopPipes::MapContext& context) {

    std::string line = context.getInputValue();

    std::string year = line.substr(15, 4);

    std::string airTemperature = line.substr(87, 5);

    std::string q = line.substr(92, 1);

    if (airTemperature != "+9999" &&

        (q == "0" || q == "1" || q == "4" || q == "5" || q == "9")) {

      context.emit(year, airTemperature);

    }

  }

};  

class MapTemperatureReducer : public HadoopPipes::Reducer {

public:

  MapTemperatureReducer(HadoopPipes::TaskContext& context) {

  }

  void reduce(HadoopPipes::ReduceContext& context) {

    int maxValue = INT_MIN;

    while (context.nextValue()) {

      maxValue = std::max(maxValue, HadoopUtils::toInt(context.getInputValue()));

    }

    context.emit(context.getInputKey(), HadoopUtils::toString(maxValue));

  }

};  

int main(int argc, char *argv[]) {

  return HadoopPipes::runTask(HadoopPipes::TemplateFactory<MaxTemperatureMapper,

                              MapTemperatureReducer>());

}  

注意：和书上不一样的地方：limit.h头文件

Makefile文件（自己进行了改动）：

.SUFFIXES:.h .c .cpp .o

CC=g++

CPPFLAGS = -m64

RM = rm

SRCS = max_temperature.cpp

PROGRAM = max_temperature

INC_PATH = -I$(HADOOP_DEV_HOME)/include

LIB_PATH = -L$(HADOOP_DEV_HOME)/lib/native

LIBS = -lhadooppipes -lcrypto -lhadooputils -lpthread

$(PROGRAM):$(SRCS)

	$(CC) $(CPPFLAGS) $(INC_PATH) $< -Wall $(LIB_PATH) $(LIBS)  -g -O2 -o $@

.PHONY:clean

clean:

	$(RM) $(PROGRAM)
	

源数据文件：

0067011990999991950051507004+68750+023550FM-12+038299999V0203301N00671220001CN9999999N9+00001+99999999999  

0043011990999991950051512004+68750+023550FM-12+038299999V0203201N00671220001CN9999999N9+00221+99999999999  

0043011990999991950051518004+68750+023550FM-12+038299999V0203201N00261220001CN9999999N9-00111+99999999999  

0043012650999991949032412004+62300+010750FM-12+048599999V0202701N00461220001CN0500001N9+01111+99999999999  

0043012650999991949032418004+62300+010750FM-12+048599999V0202701N00461220001CN0500001N9+00781+99999999999

上传到HDFS：hdfs dfs -put sample.txt

make后生成了可运行文件上传到HDFS： hdfs dfs -put max_temperature /bin

运行方法： hadoop pipes -D hadoop.pipes.java.recordreader=true -D hadoop.pipes.java.recordwriter=true -input /user/root/sample.txt -output /output -program /bin/max_temperature

数据输出结果：