Bash变量替换通过执行查找的输出

问题描述

有没有办法在 find 的输出上应用 bash 变量替换？我知道我已经看到有人在堆栈溢出，但我似乎无法找到特定的职位了。

作为一个例子，假设我想重命名文件 *。png 到 * _ copy.png 。我知道我可以使用 rename 来做到这一点，但这只是一个想法实验。

现在我想成为能够做到这样的事情：

  find。 -name* png-exec mv{}$ {{}％。*} _ copy.png\; 
  

导致无效替换。当然，我可以先将输出分配给一个变量，然后在子shell中应用替换，但是否真的是唯一的方法？

  find。 -name* .png-exec bash -c'var ={}; mv{}$ {var％。*} _ copy.png'\; 
  

或是否有任何方法可以直接从 { } ？

共识

Etan Reisner 指出，处理find输出的更好更安全的方法是将其作为位置参数传递。

 查找。 -name* .png-exec bash -cmv$ 0$ {0％。*} _ copy.png'{}\; 
  

解决方案

我花了一段时间才得到问题。基本上你是问如果是这样的：
$ b $ pre $ echo$ {test.png％.png}


code>

可以用于获取单词 test 。

答案是否定的。以 $ {开头的， / code>是参数替换运算符。它们只能用于变量，而不能用于字符串，这意味着您需要将字符串存储在变量中。像这样：



  img =test.png
 echo$ {img％.png}
  





---

只为Google的游客，我会用重命名为这个特定的任务。 （正如OP在他的问题中已经提到的那样）。命令可能如下所示：

  find -name'* png'-execdir rename's / \.png / _copy .png /'{} + 
  

Is there any way to apply bash variable substitution on find's output? I know I've seen some one do it on stack overflow but I can't seem to find that particular post anymore.

As an example, let's say I want to rename files *.png to *_copy.png. I know I can do this using rename but it's just a thought experiment.

Now I'd like to be able to do something like this:

find . -name "*png" -exec mv "{}" "${{}%.*}_copy.png" \;

Which results in an invalid substitution. Of course, I could first assign the output to a variable and then apply substitution in a sub-shell, but is this really the only way?

find . -name "*.png" -exec bash -c 'var="{}";  mv "{}" "${var%.*}_copy.png"' \;

Or is there any way this can be achieved directly from {}?

Consensus

As Etan Reisner remarked, a better and safer way to handle the output of find would be to pass it as positional argument.

find . -name "*.png" -exec bash -c 'mv "$0" "${0%.*}_copy.png"' "{}" \;

解决方案

It took me a while to get the question. Basically you are asking if something like:

echo "${test.png%.png}"

could be used to get the word test.

The answer is no. The string manipulation operators starting with ${ are a subset of the parameter substitution operators. They work only on variables, not with string literals, meaning you need to store the string in a variable before. Like this:

img="test.png"
echo "${img%.png}"

---

Just for travellers from Google, I would use rename for this particular task. (As the OP already mentioned in his question). The command could look like this:

find -name '*png' -execdir rename 's/\.png/_copy.png/' {} +

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