如果只想append操作：
1. echo "<Text to append>" | hdfs dfs -appendToFile - yourHdfsPath/test.txt
如果想modify操作：
1 hdfs dfs -get yourHdfsPath/test.txt 2 vi test.txt #or use any other tool and modify it 3 hdfs dfs -put -f test.txt yourHdfsPath/test.txt