第2章 Hadoop快速入门
2.5 WordContent简单应用
Hadoop的HelloWorld程序
2.5.1 创建HDFS目录
hdfs命令位于bin目录下，通过hdfs dfs -mkdir命令可以创建一个目录。
[root@node1 hadoop-2.7.3]# bin/hdfs dfs -mkdir -p inputhdfs创建的目录默认会放到/user/{username}/目录下面，其中{username}是当前用户名。所以input目录应该在/user/root/下面。
下面通过｀hdfs dfs -ls｀命令可以查看HDFS目录文件
[root@node1 hadoop-2.7.3]# bin/hdfs dfs -ls /
2.5.2 上传文件到HDFS
在本地新建一个文本文件
vi /root/words.txt
[root@node1 hadoop-2.7.3]# vi /root/words.txt随便输入几个单词，保存退出。
将本地文件/root/words.txt上传到HDFS bin/hdfs dfs -put /root/words.txt input bin/hdfs dfs -ls input
2.5.3 运行WordContent
执行下面命令：
bin/hadoop jar share/hadoop/mapreduce/hadoop-mapreduce-examples-2.7.3.jar wordcount input output
[root@node1 hadoop-2.7.3]# bin/hadoop jar share/hadoop/mapreduce/hadoop-mapreduce-examples-2.7.3.jar wordcount input output
17/05/12 09:04:39 INFO client.RMProxy: Connecting to ResourceManager at /0.0.0.0:8032
17/05/12 09:04:41 INFO input.FileInputFormat: Total input paths to process : 1
17/05/12 09:04:41 INFO mapreduce.JobSubmitter: number of splits:1
17/05/12 09:04:42 INFO mapreduce.JobSubmitter: Submitting tokens for job: job_1494590593576_0001
17/05/12 09:04:43 INFO impl.YarnClientImpl: Submitted application application_1494590593576_0001
17/05/12 09:04:43 INFO mapreduce.Job: The url to track the job: http://node1:8088/proxy/application_1494590593576_0001/
17/05/12 09:04:43 INFO mapreduce.Job: Running job: job_1494590593576_0001
17/05/12 09:05:08 INFO mapreduce.Job: Job job_1494590593576_0001 running in uber mode : false
17/05/12 09:05:08 INFO mapreduce.Job: map 0% reduce 0%
17/05/12 09:05:19 INFO mapreduce.Job: map 100% reduce 0%
17/05/12 09:05:31 INFO mapreduce.Job: map 100% reduce 100%
17/05/12 09:05:32 INFO mapreduce.Job: Job job_1494590593576_0001 completed successfully
17/05/12 09:05:32 INFO mapreduce.Job: Counters: 49
File System Counters
FILE: Number of bytes read=54
FILE: Number of bytes written=237325
FILE: Number of read operations=0
FILE: Number of large read operations=0
FILE: Number of write operations=0
HDFS: Number of bytes read=163
HDFS: Number of bytes written=32
HDFS: Number of read operations=6
HDFS: Number of large read operations=0
HDFS: Number of write operations=2
Job Counters
Launched map tasks=1
Launched reduce tasks=1
Data-local map tasks=1
Total time spent by all maps in occupied slots (ms)=8861
Total time spent by all reduces in occupied slots (ms)=8430
Total time spent by all map tasks (ms)=8861
Total time spent by all reduce tasks (ms)=8430
Total vcore-milliseconds taken by all map tasks=8861
Total vcore-milliseconds taken by all reduce tasks=8430
Total megabyte-milliseconds taken by all map tasks=9073664
Total megabyte-milliseconds taken by all reduce tasks=8632320
Map-Reduce Framework
Map input records=3
Map output records=9
Map output bytes=91
Map output materialized bytes=54
Input split bytes=108
Combine input records=9
Combine output records=4
Reduce input groups=4
Reduce shuffle bytes=54
Reduce input records=4
Reduce output records=4
Spilled Records=8
Shuffled Maps =1
Failed Shuffles=0
Merged Map outputs=1
GC time elapsed (ms)=249
CPU time spent (ms)=2950
Physical memory (bytes) snapshot=303017984
Virtual memory (bytes) snapshot=4157116416
Total committed heap usage (bytes)=165810176
Shuffle Errors
BAD_ID=0
CONNECTION=0
IO_ERROR=0
WRONG_LENGTH=0
WRONG_MAP=0
WRONG_REDUCE=0
File Input Format Counters
Bytes Read=55
File Output Format Counters
Bytes Written=322.5.4 查看结果
bin/hdfs dfs -ls output
bin/hdfs dfs -cat output/part-r-00000
[root@node1 hadoop-2.7.3]# bin/hdfs dfs -ls output/
Found 2 items
-rw-r--r-- 1 root supergroup 0 2017-05-12 09:05 output/_SUCCESS
-rw-r--r-- 1 root supergroup 32 2017-05-12 09:05 output/part-r-00000
[root@node1 hadoop-2.7.3]# bin/hdfs dfs -cat output/part-r-00000
Hadoop 3
Hello 2
Java 2
World 2
[root@node1 hadoop-2.7.3]# 