Hadoop实战 Hadoop Pipes运行C++程序问题解决，hadooppipes
Hadoop实战 Hadoop Pipes运行C++程序问题解决，hadooppipes
说明：我使用的是hadoop-1.2.1，开发环境是OpenSuSE12.3 x64。 Hadoop安装在/usr/lib/hadoop下。并且我的hadoop的相关指令已经加入到了系统的path中。
下面四篇有我解决问题时，所主要参考的文档：
1、http://www.cnblogs.com/lanxuezaipiao/p/3648853.html 该博客指出64位的libhadooppipes.a和 libhadooputils.a这两个库应该由我们自己编译，官方提供的是32位的库。
2、http://guoyunsky.iteye.com/blog/1709654
3、http://blog.csdn.net/keljony/article/details/29872915
4、http://blog.csdn.net/sigxxl/article/details/12293435
第二、三、四篇博客指出了如何解决“Hadoop Pipes “Server failed to authenticate”错误，这也是我们的主要内容。
这里所说的是《hadoop实战》（第2版）中3.5节Hadoop Pipes的例子。
（1）下面附上书上的wordcount.cpp的代码，这里我完全基本完全照着书上敲的，为了方便只在前面加了名using namespace std;另外加了<vector>的头文件。
#include "hadoop/Pipes.hh"
#include "hadoop/TemplateFactory.hh"
#include "hadoop/StringUtils.hh"
#include <vector>
using namespace std;
const std::string WORDCOUNT = "WORDCOUNT";
const std::string INPUT_WORDS = "INPUT_WORDS";
const std::string OUTPUT_WORDS = "OUTPUT_WORDS";
class WordCountMap : public HadoopPipes::Mapper
{
public:
HadoopPipes::TaskContext::Counter* inputWords;
WordCountMap(HadoopPipes::TaskContext& context)
{
inputWords = context.getCounter(WORDCOUNT, INPUT_WORDS);
}
void map(HadoopPipes::MapContext& context)
{
vector<string> words = HadoopUtils::splitString(context.getInputValue(), " ");
for(unsigned int i = 0; i < words.size(); ++i)
{
context.emit(words[i], "1");
}
context.incrementCounter(inputWords, words.size());
}
};
class WordCountReduce : public HadoopPipes::Reducer
{
public:
HadoopPipes::TaskContext::Counter* outputWords;
WordCountReduce(HadoopPipes::TaskContext& context)
{
outputWords = context.getCounter(WORDCOUNT, OUTPUT_WORDS);
}
void reduce(HadoopPipes::ReduceContext& context)
{
int sum = 0;
while(context.nextValue())
{
sum += HadoopUtils::toInt(context.getInputValue());
}
context.emit(context.getInputKey(), HadoopUtils::toString(sum));
context.incrementCounter(outputWords, 1);
}
};
int main(int argc, char* argv[])
{
return HadoopPipes::runTask(HadoopPipes::TemplateFactory<WordCountMap, WordCountReduce>());
}
HADOOP_INSTALL=/usr/lib/hadoop-1.2.1
PLATFORM=Linux-i386-32
CC=g++
CPPFLAGS= -m32 -I$(HADOOP_INSTALL)/c++/$(PLATFORM)/include
wordcount: wordcount.cpp
$(CC) ${CPPFLAGS} $< -Wall -L$(HADOOP_INSTALL)/c++/$(PLATFORM)/lib -lhadooppipes -lhadooputils -lpthread -g -O2 -o $@
clean:
rm -f *.o wordcount
由于默认使用的库是32位的，如果你用的是64位的系统，应该将
PLATFORM=Linux-i386-32修改为
Linux-amd64-64。这里书上说得有点问题，书上说的是“如果是AMD的CPU，请使用Linux-amd64-64”,这里应该是如果是64位的系统的话，请使用Linux-amd64-64。并将
CPPFLAGS= -m32 -I$(HADOOP_INSTALL)/c++/$(PLATFORM)/include
改为
CPPFLAGS= -m64 -I$(HADOOP_INSTALL)/c++/$(PLATFORM)/include
修改完成后，输入make进行编译会报如下的错误：
g++ -m64 -I/usr/lib/hadoop-1.2.1/c++/Linux-amd64-64/include wordcount.cpp -Wall -L/usr/lib/hadoop-1.2.1/c++/Linux-amd64-64/lib -lhadooppipes -lhadooputils -lpthread -g -O2 -o wordcount /usr/lib/hadoop-1.2.1/c++/Linux-amd64-64/lib/libhadooppipes.a(HadoopPipes.o): In function `HadoopPipes::BinaryProtocol::createDigest(std::string&, std::string&)': /usr/lib/hadoop-1.2.1/src/c++/pipes/impl/HadoopPipes.cc:426: undefined reference to `EVP_sha1' /usr/lib/hadoop-1.2.1/src/c++/pipes/impl/HadoopPipes.cc:426: undefined reference to `HMAC_Init' /usr/lib/hadoop-1.2.1/src/c++/pipes/impl/HadoopPipes.cc:427: undefined reference to `HMAC_Update' /usr/lib/hadoop-1.2.1/src/c++/pipes/impl/HadoopPipes.cc:429: undefined reference to `HMAC_Final' /usr/lib/hadoop-1.2.1/src/c++/pipes/impl/HadoopPipes.cc:430: undefined reference to `HMAC_CTX_cleanup' /usr/lib/hadoop-1.2.1/src/c++/pipes/impl/HadoopPipes.cc:436: undefined reference to `BIO_f_base64' /usr/lib/hadoop-1.2.1/src/c++/pipes/impl/HadoopPipes.cc:436: undefined reference to `BIO_new' /usr/lib/hadoop-1.2.1/src/c++/pipes/impl/HadoopPipes.cc:437: undefined reference to `BIO_s_mem' /usr/lib/hadoop-1.2.1/src/c++/pipes/impl/HadoopPipes.cc:437: undefined reference to `BIO_new' /usr/lib/hadoop-1.2.1/src/c++/pipes/impl/HadoopPipes.cc:438: undefined reference to `BIO_push' /usr/lib/hadoop-1.2.1/src/c++/pipes/impl/HadoopPipes.cc:439: undefined reference to `BIO_write' /usr/lib/hadoop-1.2.1/src/c++/pipes/impl/HadoopPipes.cc:440: undefined reference to `BIO_ctrl' /usr/lib/hadoop-1.2.1/src/c++/pipes/impl/HadoopPipes.cc:441: undefined reference to `BIO_ctrl' /usr/lib/hadoop-1.2.1/src/c++/pipes/impl/HadoopPipes.cc:446: undefined reference to `BIO_free_all' /usr/lib/hadoop-1.2.1/src/c++/pipes/impl/HadoopPipes.cc:426: undefined reference to `EVP_sha1' /usr/lib/hadoop-1.2.1/src/c++/pipes/impl/HadoopPipes.cc:426: undefined reference to `HMAC_Init' /usr/lib/hadoop-1.2.1/src/c++/pipes/impl/HadoopPipes.cc:427: undefined reference to `HMAC_Update' /usr/lib/hadoop-1.2.1/src/c++/pipes/impl/HadoopPipes.cc:429: undefined reference to `HMAC_Final' /usr/lib/hadoop-1.2.1/src/c++/pipes/impl/HadoopPipes.cc:430: undefined reference to `HMAC_CTX_cleanup' /usr/lib/hadoop-1.2.1/src/c++/pipes/impl/HadoopPipes.cc:436: undefined reference to `BIO_f_base64' /usr/lib/hadoop-1.2.1/src/c++/pipes/impl/HadoopPipes.cc:436: undefined reference to `BIO_new' /usr/lib/hadoop-1.2.1/src/c++/pipes/impl/HadoopPipes.cc:437: undefined reference to `BIO_s_mem' /usr/lib/hadoop-1.2.1/src/c++/pipes/impl/HadoopPipes.cc:437: undefined reference to `BIO_new' /usr/lib/hadoop-1.2.1/src/c++/pipes/impl/HadoopPipes.cc:438: undefined reference to `BIO_push' /usr/lib/hadoop-1.2.1/src/c++/pipes/impl/HadoopPipes.cc:439: undefined reference to `BIO_write' /usr/lib/hadoop-1.2.1/src/c++/pipes/impl/HadoopPipes.cc:440: undefined reference to `BIO_ctrl' /usr/lib/hadoop-1.2.1/src/c++/pipes/impl/HadoopPipes.cc:441: undefined reference to `BIO_ctrl' /usr/lib/hadoop-1.2.1/src/c++/pipes/impl/HadoopPipes.cc:446: undefined reference to `BIO_free_all' collect2: error: ld returned 1 exit status make: *** [wordcount] Error 1出现该错误是因为在编译时少加了两个选项（-lcrypto -lssl）所导致的，应将
$(CC) ${CPPFLAGS} $< -Wall -L$(HADOOP_INSTALL)/c++/$(PLATFORM)/lib -lhadooppipes -lhadooputils -lpthread -g -O2 -o $@修改为
$(CC) ${CPPFLAGS} $< -lcrypto -lssl -Wall -L$(HADOOP_INSTALL)/c++/$(PLATFORM)/lib -lhadooppipes -lhadooputils -lpthread -g -O2 -o $@
这样输入make后，顺利通过了编译。下面附上我的makefile文件，这里我做了上述的修改，为了文件，我在makefile文件中多加了clean目标。
HADOOP_INSTALL=/usr/lib/hadoop-1.2.1
PLATFORM=Linux-amd64-64
CC=g++
CPPFLAGS= -m64 -I$(HADOOP_INSTALL)/c++/$(PLATFORM)/include
wordcount: wordcount.cpp
$(CC) ${CPPFLAGS} $< -lcrypto -lssl -Wall -L$(HADOOP_INSTALL)/c++/$(PLATFORM)/lib -lhadooppipes -lhadooputils -lpthread -g -O2 -o $@
clean:
rm -f *.o wordcount
（3）运行所生成的wordcount程序。
将生成的wordcount文件上传到HDFS的bin文件夹下。使用下面命令的建立bin文件夹并上传文件。
hadoop dfs -mkdir bin hadoop dfs -put wordcount bin向HDFS的input文件夹中上传所需要的输入文件，HDFS上如果已经存在output文件夹，则将其删除。这两部的指令很简单，这里就是再给出。
使用如下的指令运行HDFS的bin文件夹下的wordcount程序：
hadoop pipes -D hadoop.pipes.java.recordreader=true -D hadoop.pipes.java.recordwriter=true -input input -output output -program bin/wordcount此时会出现如下的问题：
xxl@xxl-pc:~/MapReduce/wordcount_cpp$ ~/hadoop-1.1.2/bin/hadoop pipes -D hadoop.pipes.java.recordreader=true -D hadoop.pipes.java.recordwriter=true -input /user/xxl/input/file0* -output /user/xxl/output/outputfile -program bin/wordcount 13/10/04 22:29:21 WARN mapred.JobClient: No job jar file set. User classes may not be found. See JobConf(Class) or JobConf#setJar(String). 13/10/04 22:29:22 INFO util.NativeCodeLoader: Loaded the native-hadoop library 13/10/04 22:29:22 WARN snappy.LoadSnappy: Snappy native library not loaded 13/10/04 22:29:22 INFO mapred.FileInputFormat: Total input paths to process : 2 13/10/04 22:29:22 INFO mapred.JobClient: Running job: job_201310041509_0017 13/10/04 22:29:23 INFO mapred.JobClient: map 0% reduce 0% 13/10/04 22:29:32 INFO mapred.JobClient: Task Id : attempt_201310041509_0017_m_000000_0, Status : FAILED java.io.IOException at org.apache.hadoop.mapred.pipes.OutputHandler.waitForAuthentication(OutputHandler.java:188) at org.apache.hadoop.mapred.pipes.Application.waitForAuthentication(Application.java:194) at org.apache.hadoop.mapred.pipes.Application.<init>(Application.java:149) at org.apache.hadoop.mapred.pipes.PipesMapRunner.run(PipesMapRunner.java:68) at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:436) at org.apache.hadoop.mapred.MapTask.run(MapTask.java:372) at org.apache.hadoop.mapred.Child$4.run(Child.java:255) at java.security.AccessController.doPrivileged(Native Method) at javax.security.auth.Subject.doAs(Subject.java:416) at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1149) at org.apache.hadoop.mapred.Child.main(Child.java:249) attempt_201310041509_0017_m_000000_0: Server failed to authenticate. Exiting 13/10/04 22:29:32 INFO mapred.JobClient: Task Id : attempt_201310041509_0017_m_000001_0, Status : FAILED java.io.IOException at org.apache.hadoop.mapred.pipes.OutputHandler.waitForAuthentication(OutputHandler.java:188) at org.apache.hadoop.mapred.pipes.Application.waitForAuthentication(Application.java:194) at org.apache.hadoop.mapred.pipes.Application.<init>(Application.java:149) at org.apache.hadoop.mapred.pipes.PipesMapRunner.run(PipesMapRunner.java:68) at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:436) at org.apache.hadoop.mapred.MapTask.run(MapTask.java:372) at org.apache.hadoop.mapred.Child$4.run(Child.java:255) at java.security.AccessController.doPrivileged(Native Method) at javax.security.auth.Subject.doAs(Subject.java:416) at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1149) at org.apache.hadoop.mapred.Child.main(Child.java:249) attempt_201310041509_0017_m_000001_0: Server failed to authenticate. Exiting 13/10/04 22:29:40 INFO mapred.JobClient: Task Id : attempt_201310041509_0017_m_000000_1, Status : FAILED java.io.IOException at org.apache.hadoop.mapred.pipes.OutputHandler.waitForAuthentication(OutputHandler.java:188) at org.apache.hadoop.mapred.pipes.Application.waitForAuthentication(Application.java:194) at org.apache.hadoop.mapred.pipes.Application.<init>(Application.java:149) at org.apache.hadoop.mapred.pipes.PipesMapRunner.run(PipesMapRunner.java:68) at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:436) at org.apache.hadoop.mapred.MapTask.run(MapTask.java:372) at org.apache.hadoop.mapred.Child$4.run(Child.java:255) at java.security.AccessController.doPrivileged(Native Method) at javax.security.auth.Subject.doAs(Subject.java:416) at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1149) at org.apache.hadoop.mapred.Child.main(Child.java:249) attempt_201310041509_0017_m_000000_1: Server failed to authenticate. Exiting 13/10/04 22:29:40 INFO mapred.JobClient: Task Id : attempt_201310041509_0017_m_000001_1, Status : FAILED java.io.IOException at org.apache.hadoop.mapred.pipes.OutputHandler.waitForAuthentication(OutputHandler.java:188) at org.apache.hadoop.mapred.pipes.Application.waitForAuthentication(Application.java:194) at org.apache.hadoop.mapred.pipes.Application.<init>(Application.java:149) at org.apache.hadoop.mapred.pipes.PipesMapRunner.run(PipesMapRunner.java:68) at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:436) at org.apache.hadoop.mapred.MapTask.run(MapTask.java:372) at org.apache.hadoop.mapred.Child$4.run(Child.java:255) at java.security.AccessController.doPrivileged(Native Method) at javax.security.auth.Subject.doAs(Subject.java:416) at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1149) at org.apache.hadoop.mapred.Child.main(Child.java:249) attempt_201310041509_0017_m_000001_1: Server failed to authenticate. Exiting 13/10/04 22:29:48 INFO mapred.JobClient: Task Id : attempt_201310041509_0017_m_000000_2, Status : FAILED java.io.IOException at org.apache.hadoop.mapred.pipes.OutputHandler.waitForAuthentication(OutputHandler.java:188) at org.apache.hadoop.mapred.pipes.Application.waitForAuthentication(Application.java:194) at org.apache.hadoop.mapred.pipes.Application.<init>(Application.java:149) at org.apache.hadoop.mapred.pipes.PipesMapRunner.run(PipesMapRunner.java:68) at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:436) at org.apache.hadoop.mapred.MapTask.run(MapTask.java:372) at org.apache.hadoop.mapred.Child$4.run(Child.java:255) at java.security.AccessController.doPrivileged(Native Method) at javax.security.auth.Subject.doAs(Subject.java:416) at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1149) at org.apache.hadoop.mapred.Child.main(Child.java:249) attempt_201310041509_0017_m_000000_2: Server failed to authenticate. Exiting 13/10/04 22:29:48 INFO mapred.JobClient: Task Id : attempt_201310041509_0017_m_000001_2, Status : FAILED java.io.IOException at org.apache.hadoop.mapred.pipes.OutputHandler.waitForAuthentication(OutputHandler.java:188) at org.apache.hadoop.mapred.pipes.Application.waitForAuthentication(Application.java:194) at org.apache.hadoop.mapred.pipes.Application.<init>(Application.java:149) at org.apache.hadoop.mapred.pipes.PipesMapRunner.run(PipesMapRunner.java:68) at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:436) at org.apache.hadoop.mapred.MapTask.run(MapTask.java:372) at org.apache.hadoop.mapred.Child$4.run(Child.java:255) at java.security.AccessController.doPrivileged(Native Method) at javax.security.auth.Subject.doAs(Subject.java:416) at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1149) at org.apache.hadoop.mapred.Child.main(Child.java:249) attempt_201310041509_0017_m_000001_2: Server failed to authenticate. Exiting 13/10/04 22:29:59 INFO mapred.JobClient: Job complete: job_201310041509_0017 13/10/04 22:29:59 INFO mapred.JobClient: Counters: 7 13/10/04 22:29:59 INFO mapred.JobClient: Job Counters 13/10/04 22:29:59 INFO mapred.JobClient: SLOTS_MILLIS_MAPS=65416 13/10/04 22:29:59 INFO mapred.JobClient: Total time spent by all reduces waiting after reserving slots (ms)=0 13/10/04 22:29:59 INFO mapred.JobClient: Total time spent by all maps waiting after reserving slots (ms)=0 13/10/04 22:29:59 INFO mapred.JobClient: Launched map tasks=8 13/10/04 22:29:59 INFO mapred.JobClient: Data-local map tasks=8 13/10/04 22:29:59 INFO mapred.JobClient: SLOTS_MILLIS_REDUCES=0 13/10/04 22:29:59 INFO mapred.JobClient: Failed map tasks=1 13/10/04 22:29:59 INFO mapred.JobClient: Job Failed: # of failed Map Tasks exceeded allowed limit. FailedCount: 1. LastFailedTask: task_201310041509_0017_m_000000 Exception in thread "main" java.io.IOException: Job failed! at org.apache.hadoop.mapred.JobClient.runJob(JobClient.java:1327) at org.apache.hadoop.mapred.pipes.Submitter.runJob(Submitter.java:248) at org.apache.hadoop.mapred.pipes.Submitter.run(Submitter.java:479) at org.apache.hadoop.mapred.pipes.Submitter.main(Submitter.java:494)该问题的主要意思是说“Server failed to authenticate”。我在最前面列出的后三篇博客主要也就是解决该问题。但上述三个解决方法还有点不足。 这里我说的是我的解决步骤。
出现该问题主要原因是所使用的库不对，官方默认是32位的，64位的需要自己编译，并将库放在合适的位置。我使用的就是64位系统，需要自己编译所需要的pipes库和util库。
1、编译pipes所需库
进入到pipes源码所在的的文件夹，我这里是/usr/lib/hadoop-1.2.1/src/c++/pipes。执行下面的命令编译生成所需要的libhadooppipes.a。
./configure make install
我在编译pipes时，未出现什么问题。完成后，会在该目录下，看到所生成的libhadooppipes.a库。下面需要将其放到wordcount程序所引用的位置或者修改wordcount的makefile文件中所引用的库的位置。这里我选择前者。将libhadooppipes.a库文件复制到wordcount中makefile所引用的位置/usr/lib/hadoop-1.2.1/c++/Linux-amd64-64/lib/ 目录下。为了安全，我也将/usr/lib/hadoop-1.2.1/src/c++/pipes/api/hadoop/目录下的两个头文件Pipes.hh和TemplateFactory.hh复制到/usr/lib/hadoop-1.2.1/c++/Linux-amd64-64/include/ 目录下。
2、编译utils所需库
进入到utils源码所在的的文件夹，我这里是/usr/lib/hadoop-1.2.1/src/c++/utils。执行下面的命令编译生成所需要的libhadooputilss.a。
./configure make install
我在编译utils时，输入./configure出现如下问题。
hadoop@keljony-laptop:/usr/local/hadoop/src/c++/pipes$ ./configure checking for a BSD-compatible install... /usr/bin/install -c checking whether build environment is sane... yes checking for gawk... no checking for mawk... mawk checking whether make sets $(MAKE)... yes checking for style of include used by make... GNU checking for gcc... gcc checking for C compiler default output file name... a.out checking whether the C compiler works... yes checking whether we are cross compiling... no checking for suffix of executables... checking for suffix of object files... o checking whether we are using the GNU C compiler... yes checking whether gcc accepts -g... yes checking for gcc option to accept ISO C89... none needed checking dependency style of gcc... gcc3 checking how to run the C preprocessor... gcc -E checking for grep that handles long lines and -e... /bin/grep checking for egrep... /bin/grep -E checking for ANSI C header files... yes checking for sys/types.h... yes checking for sys/stat.h... yes checking for stdlib.h... yes checking for string.h... yes checking for memory.h... yes checking for strings.h... yes checking for inttypes.h... yes checking for stdint.h... yes checking for unistd.h... yes checking minix/config.h usability... no checking minix/config.h presence... no checking for minix/config.h... no checking whether it is safe to define __EXTENSIONS__... yes checking for special C compiler options needed for large files... no checking for _FILE_OFFSET_BITS value needed for large files... 64 checking pthread.h usability... yes checking pthread.h presence... yes checking for pthread.h... yes checking for pthread_create in -lpthread... yes checking for HMAC_Init in -lssl... no configure: error: Cannot find libssl.so ./configure: line 5166: exit: please: numeric argument required ./configure: line 5166: exit: please: numeric argument required hadoop@keljony-laptop:/usr/local/hadoop/src/c++/pipes$主要意思是说“error: Cannot find libssl.so”。输入rpm -qa | grep ssl后，发现我已经安装了所需要的openssl等。后来在网上找到了解决方法。这里需要修改congigure文件。
我修改的是4744和4804两行的
LIBS="-lssl $LIBS"修改为
LIBS="-lssl -lcrypto $LIBS"这里你应该根据自己的情况，在configure文件中搜索LIBS="-lssl $LIBS"，然后，进行修改。行数可能和我的不同。
修改完成后再次输入./configure，检查通过。
然后输入make进行编译，此时报错，有一个cc文件中的sleep(）等函数未定义，打开该文件后，在头文件中加上#include <unistd.h>后问题得以解决。
再次输入make后，编译通过，得到所需要的libhadooputils.a库文件。
完成后，会在该目录下，看到所生成的libhadooputils.a库。下面需要将其放到wordcount程序所引用的位置或者修改wordcount的makefile文件中所引用的库的位置。这里我选择前者。将libhadooputils.a库文件复制到wordcount中makefile所引用的位置/usr/lib/hadoop-1.2.1/c++/Linux-amd64-64/lib/ 目录下。为了安全，我也将/usr/lib/hadoop-1.2.1/src/c++/pipes/api/hadoop/目录下的两个头文件SerialUtils.hh和StringUtils.hh复制到/usr/lib/hadoop-1.2.1/c++/Linux-amd64-64/include/ 目录下。
（4）至此，问题全部解决。
删除HDFS上的output文件夹后。重新编译生成wordcount程序，并将其上传到HDFS的bin文件夹下（原来的wordcount程序，是用旧库编译的，不能使用）。再次运行wordcount程序，得到所需要的结果。
hadoop dfs -rmr output make //在wordcountt程序所在的文件夹中执行，使用makefile文件产生wordcount程序 hadoop dfs -rm output/worcount //删除HDFS的bin文件夹下的原有的wordcount程序 hadooop dfs -put worcount output hadoop pipes -D hadoop.pipes.java.recordreader=true -D hadoop.pipes.java.recordwriter=true -input input -output output -program bin/wordcount
从解决问题的过程，可以看出，源码有时也是会有些小错误的，我们不要因为是源码，就觉得它一定是对的，而害怕对其进行修改。解决问题的过程，也是进步的过程。
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