Some specify file paths on your system, but others adjust levers and knobs deep inside Hadoop's guts.
一些变量指定系统上的文件路径，而其他变量对Hadoop的内部进行深入的调整。
2
Is similar to the preceding method but gives you two additional parameters to specify visit options and how many directories deep into the file tree the traversal should go.
与前面的方法相似，但是它给出两个附加的参数来指定访问选项，以及遍历将访问文件树中的多少个目录。
3
Another scenario is that you have a deep nested file that you want to access quickly instead of traverse through one branch by one branch.