如何在GitHub上的别人的分支上获取分支？(How do I fetch a branch on someone else's fork on GitHub? [duplicate])

 我会说这更多的是效率 - 通过linux头命令管理hadoop fs -cat的输出可以轻松地复制一个头。 
 
hadoop fs -cat /path/to/file | head
 
 这是有效的，因为在输出所需数量的行之后，头将关闭底层流 
 
 以这种方式使用尾巴的效率要低得多 - 因为您必须流过整个文件（所有HDFS块）才能找到最终的x行数。 
 
hadoop fs -cat /path/to/file | tail
 
 hadoop fs -tail命令可以在最后一个千字节的hadoop上有效地找到最后一个块，并跳到最后一个千字节的位置，然后输出输出。 通过尾巴的管道不能轻易做到这一点。 

I would say it's more to do with efficiency - a head can easily be replicated by piping the output of a hadoop fs -cat through the linux head command.
 
hadoop fs -cat /path/to/file | head
 
This is efficient as head will close out the underlying stream after the desired number of lines have been output
 
Using tail in this manner would be considerably less efficient - as you'd have to stream over the entire file (all HDFS blocks) to find the final x number of lines.
 
hadoop fs -cat /path/to/file | tail
 
The hadoop fs -tail command as you note works on the last kilobyte - hadoop can efficiently find the last block and skip to the position of the final kilobyte, then stream the output. Piping via tail can't easily do this.