双星号通配符是什么意思? [英] What do double-asterisk wildcards mean?

问题描述

我尝试了以下命令，但无法解释它:

I've tried the following command but I am having trouble interpreting it:

ls **

但是我不确定输出的是什么，为什么会这样.

but I'm not sure exactly what it is outputting and why that is the result.

推荐答案

它可能是某些shell的特殊功能，它允许**进行递归匹配，而不是单个*，后者仅在当前目录.

It's probably using a special feature of some shells that lets ** do a recursive match, as opposed to a single *, which matches only in the current directory.

通配符*匹配当前目录中的任何文件或目录(其名称不以.开头).

The wildcard * matches any file or directory (whose name doesn't start with .) in the current directory.

** 可能与*等效，具体取决于您所使用的shell和设置.它可以匹配零个或多个字符，然后匹配零个或多个字符，这与匹配零个或多个字符一次相同.

Depending on which shell you're using, and with which settings, ** may be equivalent to *; it could match zero or more characters followed by zero or more characters, which is the same as matching zero or more characters just once.

但是对于某些外壳程序和某些设置，**是*的递归版本，匹配当前目录和子目录中的所有文件和目录.

But with some shells, with some settings, ** is a recursive version of *, matching all files and directories in the current directory and subdirectories.

引用 bash手册:

`*'
匹配任何字符串，包括空字符串.当...的时候 启用了"globstar" shell选项，并在文件名中使用了"*" 扩展上下文，两个相邻的`*用作单个模式 匹配所有文件以及零个或多个目录和子目录. 如果后接`/'，则两个相邻的``*'仅匹配 目录和子目录.

`*'
Matches any string, including the null string. When the `globstar' shell option is enabled, and `*' is used in a filename expansion context, two adjacent `*'s used as a single pattern will match all files and zero or more directories and subdirectories. If followed by a `/', two adjacent ``*'s will match only directories and subdirectories.

仅当通过以下方式设置globstar选项时，此方法才有效:

This works only if the globstar option is set via:

shopt -s globstar

(默认情况下处于禁用状态)，并且仅在相对较新的bash版本中.

(it's disabled by default) and only in relatively recent versions of bash.

我相信zsh也支持这种语法.

I believe zsh also supports this syntax.

请记住，通配符是由Shell而不是ls命令扩展的，这一点很重要.如果键入ls **或ls *.txt，则ls命令本身将永远不会看到*字符.它只会看到扩展的文件列表，就像您在命令行上键入了整个列表一样.

It's important to keep in mind that wildcards are expanded by the shell, not by the ls command. If you type ls **, or ls *.txt, the ls command itself never sees the * characters; it only sees an expanded list of files, just as if you had typed the entire list on the command line.

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