我在http://fiware-cosmos.readthedocs.io/en/latest/user_and_programmer_manual/batch/using_hadoop_and_ecosystem/#top站点中实现了代码，该代码包括在MapReduce程序的命令行中添加参数“regex”。该程序可以很好地显示
16/06/28 17:19:47 INFO input.FileInputFormat: Total input paths to process : 1
16/06/28 17:19:47 INFO mapreduce.JobSubmitter: number of splits:1
16/06/28 17:19:48 INFO mapreduce.JobSubmitter: Submitting tokens for job: job_1448020964278_0633
16/06/28 17:19:49 INFO impl.YarnClientImpl: Submitted application application_1448020964278_0633
16/06/28 17:19:49 INFO mapreduce.Job: The url to track the job: http://co2-hdpmaster.irit.fr:8088/proxy/application_1448020964278_0633/
16/06/28 17:19:49 INFO mapreduce.Job: Running job: job_1448020964278_0633
16/06/28 17:19:59 INFO mapreduce.Job: Job job_1448020964278_0633 running in uber mode : false
16/06/28 17:19:59 INFO mapreduce.Job: map 0% reduce 0%
16/06/28 17:20:10 INFO mapreduce.Job: map 100% reduce 0%
16/06/28 17:20:19 INFO mapreduce.Job: map 100% reduce 100%
16/06/28 17:20:20 INFO mapreduce.Job: Job job_1448020964278_0633 completed successfully
16/06/28 17:20:20 INFO mapreduce.Job: Counters: 49
File System Counters
FILE: Number of bytes read=6
FILE: Number of bytes written=230845
FILE: Number of read operations=0
FILE: Number of large read operations=0
FILE: Number of write operations=0
HDFS: Number of bytes read=916
HDFS: Number of bytes written=0
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
Rack-local map tasks=1
Total time spent by all maps in occupied slots (ms)=7478
Total time spent by all reduces in occupied slots (ms)=7151
Total time spent by all map tasks (ms)=7478
Total time spent by all reduce tasks (ms)=7151
Total vcore-seconds taken by all map tasks=7478
Total vcore-seconds taken by all reduce tasks=7151
Total megabyte-seconds taken by all map tasks=22972416
Total megabyte-seconds taken by all reduce tasks=21967872
Map-Reduce Framework
Map input records=17
Map output records=0
Map output bytes=0
Map output materialized bytes=6
Input split bytes=125
Combine input records=0
Combine output records=0
Reduce input groups=0
Reduce shuffle bytes=6
Reduce input records=0
Reduce output records=0
Spilled Records=0
Shuffled Maps =1
Failed Shuffles=0
Merged Map outputs=1
GC time elapsed (ms)=114
CPU time spent (ms)=2120
Physical memory (bytes) snapshot=1398767616
Virtual memory (bytes) snapshot=6716833792
Total committed heap usage (bytes)=2156396544
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=791
File Output Format Counters
Bytes Written=0
当我想使用
hadoop dfs -cat output/part-r-00000命令显示文件内容时，它什么也不返回有人可以解释这个问题
最佳答案
您的工作没有产生任何结果:
Map output records=0
Reduce output records=0
HDFS: Number of bytes written=0
因此文件可能为空。您应该在HDFS上检查其大小以确认这一点。
关于java - “hadoop dfs -cat output”不返回任何内容，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/38098470/