运行Hadoop权威指南中的例子：3.5.2：FileSystemCat
1、编写代码：package crt.hadoop.test;
import java.io.InputStream;
import java.net.URI;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IOUtils;
public class FileSystemCat {
public static void main(String[] args) throws Exception{
String uri = args;
Configuration conf = new Configuration();
FileSystem fs = FileSystem.get(URI.create(uri), conf);
InputStream in = null;
try{
in = fs.open(new Path(uri));
IOUtils.copyBytes(in, System.out, 4096, false);
} finally{
IOUtils.closeStream(in);
}
}
}
2、把FileSystemCat.java复制到$HADOOP_HOME/build/classes/crt/hadoop/test
3、编译：
$ javac -classpath $HADOOP_HOME/hadoop-common-0.21.0.jar
$HADOOP_HOME/build/classes/crt/hadoop/test/FileSystemCat.java
4、运行：
$ export HADOOP_CLASSPATH=build/classes
$ hadoop crt.hadoop.test.FileSystemCat hdfs://hadoop-namenode:9001/tmp/readdatatest.txt
运行结果：
hello hadoop
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