在不同情况下理解Grep的选项-H的实际用法 [英] To understand the practical use of Grep's option -H in different situations

问题描述

这个问题基于这个答案。

为什么您会从两个命令中获得相同的输出？
$ b 命令A

  $ sudo grep muel * / tmp 
 masi：muel 
  
  
 
 
 
 命令B  
 $ c $ $ sudo grep -H muel * / tmp 
 masi：muel 
  

Rob的评论建议我命令A 不应该给我 masi：，但只有 muel 。

总之， -H ？

的实际用途是什么？

解决方案

如果给出多个文件名，Grep会默认列出文件名。即使只给出一个文件名， -H 选项也会这样做。在这两个例子中，给出了多个文件名。

这里有一个更好的例子：

  $ grep Richie notes.txt 
 Richie戴眼镜。 
 
 $ grep -H Richie notes.txt 
 notes.txt：Richie戴眼镜。 
  

当您为未知数量的文件提供通配符时，它会更加有用，并且您始终即使通配符只匹配一个文件，也希望打印文件名。

This question is based on this answer.

Why do you get the same output from the both commands?

Command A

$sudo grep muel *                                                             /tmp
masi:muel

Command B

$sudo grep -H muel *                                                          /tmp
masi:muel

Rob's comment suggests me that Command A should not give me masi:, but only muel.

In short, what is the practical purpose of -H?

解决方案

Grep will list the filenames by default if more than one filename is given. The -H option makes it do that even if only one filename is given. In both your examples, more than one filename is given.

Here's a better example:

$ grep Richie notes.txt
Richie wears glasses.

$ grep -H Richie notes.txt
notes.txt:Richie wears glasses.

It's more useful when you're giving it a wildcard for an unknown number of files, and you always want the filenames printed even if the wildcard only matches one file.

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