猛砸，遍历目录 [英] Bash, looping over directories

问题描述

我对如何bash的作品一个根本性的问题，和相关的实践问题。

I have a fundamental question about how bash works, and a related practical question.

最基本的问题：假设我是有三个子目录的目录：A，B和C

Fundamental question: suppose I am in a directory that has three subdirectories: a, b, and c.

母鸡code

for dir in $(ls)
do 
    echo $dir
done

吐出：

a b c
a b c
a b c

即， DIR 总是存储在我的 CWD 所有的文件/目录的列表。我的问题是：为什么在世界上会变成这样方便？在我看来，这是更为有用的，直观的让 DIR 存储每次打开一个元素，即我希望有输出

i.e, dir always stores a list of all of the files/directories in my cwd. My question is: why in the world would this be convenient? In my opinion it is far more useful and intuitive to have dir store each element at a time, i.e I would want to have output

a
b
c

此外，作为每一个答案 - 这是错误的使用在$（LS）DIR ，但是当我使用为DIR在$（ls -l命令）我得到 ABC 更显副本（以上有目录/在CWD文件）。这是为什么？

Also, as per one of the answers - it is wrong to use for dir in $(ls), but when I use for dir in $(ls -l) I get even more copies of a b c (more than there are directories/files in the cwd). Why is that?

我的第二个问题是实用：在我的我怎么遍历所有目录（而不是文件！）CWD 与资本W¯¯开始？我开始用

My second question is practical: how do I loop over all the directories (not files!) in my cwd that start with capital W? I started with

for dir in `ls -l W*`

但这种失败，因为一）问题的原因1和b），因为它不排除文件。建议AP preciated。

but this fails because a) the reason in question 1 and b) because it doesn't exclude files. Suggestions appreciated.

推荐答案

永远不要解析 LS的输出像这样（的为什么你不应该解析ls的输出结果（1））。

Never ever parse the output of ls like this (Why you shouldn't parse the output of ls(1)).

另外，你的语法是错误的。你不是说（），你的意思是 $（）。

Also, your syntax is wrong. You don't mean (), you mean $().

话虽这么说，遍历目录，开始用W，你会做（或使用找到命令来代替，这取决于您的方案）：

That being said, to loop over directories starting with W you would do (or use the find command instead, depending on your scenario):

for path in /my/path/W*; do
    [ -d "${path}" ] || continue # if not a directory, skip
    dirname="$(basename "${path}")"
    do_stuff
done

至于你从邪恶的LS-循环得到的输出，它不应该像她那样。这是预期的输出，并演示了为什么你不希望在第一时间使用LS：

As for the output you get from the evil ls-loop, it should not look like that. This is the expected output and demonstrates why you do not want to use ls in the first place:

$ find
.
./c
./a
./foo bar
./b

$ type ls
ls is hashed (/bin/ls)

$ for x in $(ls); do echo "${x}"; done
a
b
c
foo
bar

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