什么递归地扩展到当前目录中的所有文件? [英] What expands to all files in current directory recursively?

问题描述

我知道 **/*.ext 扩展到与 *.ext 匹配的所有子目录中的所有文件，但是包含所有此类文件的类似扩展是什么?当前目录也是?

解决方案

这将适用于 Bash 4:

ls -l {,**/}*.ext

为了使双星号 glob 工作，需要设置 globstar 选项(默认:开启):

shopt -s globstar

来自man bash:

<前>环球之星如果设置，文件名扩展中使用的模式**text 将匹配一个文件和零个或多个目录和子目录.如果模式后跟/，则仅目录和子目录匹配.

现在我想知道 globstar 处理中是否曾经有过错误，因为现在只使用 ls **/*.ext 我得到了正确的结果.

无论如何，我查看了 kenorb 使用 VLC 存储库所做的分析，发现该分析和我的直接在上面回答:

与 find 命令输出的比较无效，因为指定 -type f 不包括其他文件类型(特别是目录)和 ls 列出的命令可能会这样做.此外，列出的命令之一，ls -1 {,**/}*.* - 这似乎是基于我上面的，只输出名称​​包含一个点 用于子目录中的文件.OP 的问题和我的回答包含一个点，因为要查找的是具有特定扩展名的文件.

然而，最重要的是，使用带有 globstar 模式 ** 的 ls 命令存在一个特殊问题.由于模式被 Bash 扩展到被检查树中的所有文件名(和目录名)，因此出现了许多重复项.在扩展之后，ls 命令列出了每一个以及它们的内容(如果它们是目录).

示例:

在我们当前目录中是子目录A及其内容:

A└── AB└── ABC├── ABC1├── ABC2└── ABCD└── ABCD1

在那棵树中，** 扩展为AA/AB A/AB/ABC A/AB/ABC/ABC1 A/AB/ABC/ABC2 A/AB/ABC/ABCD A/AB/ABC/ABCD/ABCD1"(7 个条目).如果你执行 echo ** 这就是你得到的确切输出，并且每个条目都表示一次.但是，如果你执行ls **，它会输出每个的列表> 那些条目.所以本质上它是 ls A 后跟 ls A/AB 等，所以 A/AB 会显示两次.此外，ls 会将每个子目录的输出分开:

<代码>...<空行>目录名称:内容项内容项

因此，使用 wc -l 会计算所有这些空行和目录名称部分标题，这会使计数更远.

这是您不应该解析ls的另一个原因.

作为进一步分析的结果，我建议不要在任何情况下使用 globstar 模式，除非以这种方式迭代文件树:

用于进入**做一些$entry"完毕

作为最后的比较，我使用了一个我手边的 Bash 源代码库并这样做了:

shopt -s globstar dotglobdiff <(echo ** | tr ' ' '
') <(find . | sed 's|./||' | sort)0a1>.

我使用 tr 将空格更改为换行符，这仅在此处有效，因为没有名称包含空格.我使用 sed 从 find 的每一行输出中删除前导 ./.我对 find 的输出进行了排序，因为它通常是未排序的，并且 Bash 的 glob 扩展已经排序.如您所见，diff 的唯一输出是find 输出的当前目录..当我做 ls ** |wc -l 输出的行数几乎是原来的两倍.

I know **/*.ext expands to all files in all subdirectories matching *.ext, but what is a similar expansion that includes all such files in the current directory as well?

解决方案

This will work in Bash 4:

ls -l {,**/}*.ext

In order for the double-asterisk glob to work, the globstar option needs to be set (default: on):

shopt -s globstar

From man bash:

    globstar
                  If set, the pattern ** used in a filename expansion con‐
                  text will match a files and zero or more directories and
                  subdirectories.  If the pattern is followed by a /, only
                  directories and subdirectories match.

Now I'm wondering if there might have once been a bug in globstar processing, because now using simply ls **/*.ext I'm getting correct results.

Regardless, I looked at the analysis kenorb did using the VLC repository and found some problems with that analysis and in my answer immediately above:

The comparisons to the output of the find command are invalid since specifying -type f doesn't include other file types (directories in particular) and the ls commands listed likely do. Also, one of the commands listed, ls -1 {,**/}*.* - which would seem to be based on mine above, only outputs names that include a dot for those files that are in subdirectories. The OP's question and my answer include a dot since what is being sought is files with a specific extension.

Most importantly, however, is that there is a special issue using the ls command with the globstar pattern **. Many duplicates arise since the pattern is expanded by Bash to all file names (and directory names) in the tree being examined. Subsequent to the expansion the ls command lists each of them and their contents if they are directories.

Example:

In our current directory is the subdirectory A and its contents:

A
└── AB
    └── ABC
        ├── ABC1
        ├── ABC2
        └── ABCD
            └── ABCD1

In that tree, ** expands to "A A/AB A/AB/ABC A/AB/ABC/ABC1 A/AB/ABC/ABC2 A/AB/ABC/ABCD A/AB/ABC/ABCD/ABCD1" (7 entries). If you do echo ** that's the exact output you'd get and each entry is represented once. However, if you do ls ** it's going to output a listing of each of those entries. So essentially it does ls A followed by ls A/AB, etc., so A/AB gets shown twice. Also, ls is going to set each subdirectory's output apart:

...
<blank line>
directory name:
content-item
content-item

So using wc -l counts all those blank lines and directory name section headings which throws off the count even farther.

This a yet another reason why you should not parse ls.

As a result of this further analysis, I recommend not using the globstar pattern in any circumstance other than iterating over a tree of files in this manner:

for entry in **
do
    something "$entry"
done

As a final comparison, I used a Bash source repository I had handy and did this:

shopt -s globstar dotglob
diff <(echo ** | tr ' ' '
') <(find . | sed 's|./||' | sort)
0a1
> .

I used tr to change spaces to newlines which is only valid here since no names include spaces. I used sed to remove the leading ./ from each line of output from find. I sorted the output of find since it is normally unsorted and Bash's expansion of globs is already sorted. As you can see, the only output from diff was the current directory . output by find. When I did ls ** | wc -l the output had almost twice as many lines.

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