Hadoop测试例子wordcount

　　1、建立一个测试的目录　　

[root@localhost hadoop-1.1.1]# bin/hadoop dfs -mkdir /hadoop/input

　　2、建立测试文件

[root@localhost test]# vi test.txt

hello hadoop
hello World
Hello Java
Hey man
i am a programmer

　　3、将测试文件放到测试目录中

[root@localhost hadoop-1.1.1]# bin/hadoop dfs -put ./test/test.txt /hadoop/input

　　4、执行wordcount程序

[root@localhost hadoop-1.1.1]# bin/hadoop jar hadoop-examples-1.1.1.jar wordcount /hadoop/input/* /hadoop/output

　　　　/hadoop/output目录必须不存在，否则会报错：

org.apache.hadoop.mapred.FileAlreadyExistsException: Output directory /hadoop/output already exists

　　　　因为Hadoop执行的是耗费资源的运算，产生的结果默认是不能被覆盖的。

　　　　执行成功的话，显示下面的信息：

[root@localhost hadoop-1.1.1]# bin/hadoop jar hadoop-examples-1.1.1.jar wordcount /hadoop/input/* /hadoop/output

13/01/17 00:36:06 INFO input.FileInputFormat: Total input paths to process : 1
13/01/17 00:36:06 INFO util.NativeCodeLoader: Loaded the native-hadoop library
13/01/17 00:36:06 WARN snappy.LoadSnappy: Snappy native library not loaded
13/01/17 00:36:07 INFO mapred.JobClient: Running job: job_201301162205_0006
13/01/17 00:36:08 INFO mapred.JobClient:  map 0% reduce 0%
13/01/17 00:36:14 INFO mapred.JobClient:  map 100% reduce 0%
13/01/17 00:36:22 INFO mapred.JobClient:  map 100% reduce 33%
13/01/17 00:36:24 INFO mapred.JobClient:  map 100% reduce 100%
13/01/17 00:36:25 INFO mapred.JobClient: Job complete: job_201301162205_0006
13/01/17 00:36:25 INFO mapred.JobClient: Counters: 29
13/01/17 00:36:25 INFO mapred.JobClient:   Job Counters 
13/01/17 00:36:25 INFO mapred.JobClient:     Launched reduce tasks=1
13/01/17 00:36:25 INFO mapred.JobClient:     SLOTS_MILLIS_MAPS=6863
13/01/17 00:36:25 INFO mapred.JobClient:     Total time spent by all reduces waiting after reserving slots (ms)=0
13/01/17 00:36:25 INFO mapred.JobClient:     Total time spent by all maps waiting after reserving slots (ms)=0
13/01/17 00:36:25 INFO mapred.JobClient:     Launched map tasks=1
13/01/17 00:36:25 INFO mapred.JobClient:     Data-local map tasks=1
13/01/17 00:36:25 INFO mapred.JobClient:     SLOTS_MILLIS_REDUCES=9207
13/01/17 00:36:25 INFO mapred.JobClient:   File Output Format Counters 
13/01/17 00:36:25 INFO mapred.JobClient:     Bytes Written=78
13/01/17 00:36:25 INFO mapred.JobClient:   FileSystemCounters
13/01/17 00:36:25 INFO mapred.JobClient:     FILE_BYTES_READ=128
13/01/17 00:36:25 INFO mapred.JobClient:     HDFS_BYTES_READ=170
13/01/17 00:36:25 INFO mapred.JobClient:     FILE_BYTES_WRITTEN=48059
13/01/17 00:36:25 INFO mapred.JobClient:     HDFS_BYTES_WRITTEN=78
13/01/17 00:36:25 INFO mapred.JobClient:   File Input Format Counters 
13/01/17 00:36:25 INFO mapred.JobClient:     Bytes Read=62
13/01/17 00:36:25 INFO mapred.JobClient:   Map-Reduce Framework
13/01/17 00:36:25 INFO mapred.JobClient:     Map output materialized bytes=128
13/01/17 00:36:25 INFO mapred.JobClient:     Map input records=5
13/01/17 00:36:25 INFO mapred.JobClient:     Reduce shuffle bytes=128
13/01/17 00:36:25 INFO mapred.JobClient:     Spilled Records=22
13/01/17 00:36:25 INFO mapred.JobClient:     Map output bytes=110
13/01/17 00:36:25 INFO mapred.JobClient:     CPU time spent (ms)=1650
13/01/17 00:36:25 INFO mapred.JobClient:     Total committed heap usage (bytes)=176492544
13/01/17 00:36:25 INFO mapred.JobClient:     Combine input records=12
13/01/17 00:36:25 INFO mapred.JobClient:     SPLIT_RAW_BYTES=108
13/01/17 00:36:25 INFO mapred.JobClient:     Reduce input records=11
13/01/17 00:36:25 INFO mapred.JobClient:     Reduce input groups=11
13/01/17 00:36:25 INFO mapred.JobClient:     Combine output records=11
13/01/17 00:36:25 INFO mapred.JobClient:     Physical memory (bytes) snapshot=180088832
13/01/17 00:36:25 INFO mapred.JobClient:     Reduce output records=11
13/01/17 00:36:25 INFO mapred.JobClient:     Virtual memory (bytes) snapshot=756244480
13/01/17 00:36:25 INFO mapred.JobClient:     Map output records=12
[root@localhost hadoop-1.1.1]# 

　　5、查看结果

　　　　wordcount程序统计目标文件中的单词个数，将结果输出到/hadoop/output/part-r-00000文件中

[root@localhost hadoop-1.1.1]# bin/hadoop dfs -ls /hadoop/output

Found 3 items
-rw-r--r--   1 root supergroup          0 2013-01-17 00:36 /hadoop/output/_SUCCESS
drwxr-xr-x   - root supergroup          0 2013-01-17 00:36 /hadoop/output/_logs
-rw-r--r--   1 root supergroup         78 2013-01-17 00:36 /hadoop/output/part-r-00000
[root@localhost hadoop-1.1.1]#

[root@localhost hadoop-1.1.1]# bin/hadoop dfs -cat /hadoop/output/part-r-00000

Hello   1
Hey     1
Java    1
World   1
a       1
am      1
hadoop  1
hello   2
i       1
man     1
programmer      1
[root@localhost hadoop-1.1.1]#