Hadoop HDFS命令学习笔记

cat

Usage: hadoop fs -cat [-ignoreCrc] URI [URI ...]

Copies source paths to stdout.

Options

• The -ignoreCrc option disables checkshum verification.

Example:

• hadoop fs -cat hdfs://nn1.example.com/file1 hdfs://nn2.example.com/file2
• hadoop fs -cat file:///file3 /user/hadoop/file4

Exit Code:

Returns 0 on success and -1 on error.

eg：

hadoop fs -cat /work/songwang4/kg/repair/result/sourceMovie/res/part* | grep results | wc -l

统计该路径下文件中含有多少 results字段

hadoop fs -cat /work/songwang4/kg/repair/result/sourceMovie/res/part* | grep -v results | wc -l

统计该路径下文件中含有多少没包含 results字段

hadoop fs -cat /work/songwang4/kg/repair/result/sourceMovie/res/part* | grep results > result.json

多个文件合并为一个

hadoop fs -put new1v1.json /work/songwang4/kg/repair/data/relation

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