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translating---geekpi
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Linux command line navigation tips: the basics of pushd and popd commands
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============================================================
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### On this page
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1. [The basics of pushd and popd commands][1]
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2. [Some advanced points][2]
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3. [Conclusion][3]
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In the [first part][4] of this series, we focused on the command line navigation aspect in Linux by discussing the usage of the **cd -** command. Some other related points/concepts were also discussed. Taking the discussion further, in this article, we will be discussing how you can have a faster navigation experience on the Linux command line using the pushd and popd commands.
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Before we move ahead, it's worth sharing that all the instructions and commands mentioned henceforth have been tested on Ubuntu 14.04 and Bash shell (version 4.3.11).
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### The basics of pushd and popd commands
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To better understand what exactly pushd and popd commands do, let's first discuss the concept of stack. Imagine an empty area on your kitchen slab, and now imagine a set of plates that you want to keep there. What will you do? Simple, keep them one over the other.
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So at the end of the whole process, the first plate that you kept on the slab ends being the last plate in the pile, and the last plate that you had in your hand ends up being the first plate in the pile. Now, when you require a plate, you pick the one which is at the top of the pile, use it, and then pick the next one when required.
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Similar is the concept of pushd and popd commands. There's a directory stack on your Linux system where you can pile up directory paths for future use. You can quickly see the contents of the stack at any point in time using the **dirs** command.
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Here's an example that shows the output of the dirs command on my system immediately after the command line terminal was launched:
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$ dirs
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~
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The tilde (~) in the output means the directory stack currently only contains the user's home directory.
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Moving on, the operation of storing a directory path and removing it are performed using the pushd and popd commands. Using pushd is very easy - just pass the path that you want to store in the directory stack as an argument to this command. Here's an example:
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pushd /home/himanshu/Downloads/
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What the above command does is, it changes your present working directory to the directory that you've passed as the argument, and also adds the path to the directory stack. To make things convenient for the user, the pushd command produces the contents of the directory stack in its output. So, when the above command was run, the following output was produced:
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```
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~/Downloads ~
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```
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The output reveals that now there are two directory paths in the stack: one is the user's home directory and other is the user's Downloads directory. The order in which they are kept is: the home directory is at the bottom and the newly-added Downloads directory is above it.
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To verify that what pushd is saying in its output is true, you can also use the dirs command:
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$ dirs
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~/Downloads ~
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So you can see that the dirs command also produced the same output.
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Let's issue a couple of more pushd commands:
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$ pushd /usr/lib/; pushd /home/himanshu/Desktop/
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/usr/lib ~/Downloads ~
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~/Desktop /usr/lib ~/Downloads ~
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So the directory stack now contains a total of four directory paths, where the home directory (~) is at the bottom, and the user's Desktop directory is at the top.
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Always keep in mind that the head of the stack is the directory that you're currently in. This means that now our current working directory is ~/Desktop.
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Now, suppose you want to go back to the /usr/lib directory, so all you have to do is to execute the popd command:
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$ popd
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/usr/lib ~/Downloads ~
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The popd command will not only switch your current directory to /usr/lib, it'll also remove ~/Desktop from the directory stack - as evident by the output the command produced. This way, the popd command will let you navigate these directories in the reverse order.
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### Some advanced points
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Now that we have discussed the basics of pushd and popd commands, let's move on to some other details related to these commands. To begin with, these commands also let you manipulate the directory stack. For example, suppose here's what your directory stack looks like:
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$ dirs
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~/Desktop /usr/lib ~ ~/Downloads
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Now, let's say the requirement is to change the order of the directory paths in the stack in a way that the topmost element (~/Desktop) comes at the bottom and rest all move up by one place each. This can be achieved using the following command:
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pushd +1
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And here's what the above command does to the directory stack:
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$ dirs
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/usr/lib ~ ~/Downloads ~/Desktop
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So we see that the order of elements in directory stack has been changed, and is now the same as we wanted. Of course, you can make the directory stack elements move any number of times. For example, the following command will move them up two times:
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$ pushd +2
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~/Downloads ~/Desktop /usr/lib ~
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You can use negative indexes as well:
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$ pushd -1
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/usr/lib ~ ~/Downloads ~/Desktop
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Similarly, you can use this technique with the popd command to remove any entry from the directory stack without leaving your current working directory. For example, if you want to remove the third entry from top (which is ~/Downloads currently) using popd, the you can run the following command:
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popd +2
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Keep in mind that the stack index begins with 0, so we've used 2 to access third entry.
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So the directory stack now contains:
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$ dirs
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/usr/lib ~ ~/Desktop
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Confirming that the entry has been removed.
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If, for some reason, you find it difficult to remember the order in which elements are positioned in the directory stack as well as the indexes they carry, you can use the -v command line option with the dirs command. Here's an example:
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$ dirs -v
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0 /usr/lib
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1 ~
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2 ~/Desktop
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As you would have probably gussed, the numbers on the left are indexes and what follows them is the directory path positioned at that index.
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**Note**: Use the -c command line option with the dirs command to clear the directory stack.
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Now let's briefly discuss the practical usage of popd and pushd commands. While they may seem a bit complicated to use in first glance, these commands come in handy while writing shell scripts - you don't need to remember where you're coming from; just do a popd and you're back to the directory where you came from.
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Experienced script writers usually use these command in the following way:
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`popd >/dev/null 2>&1`
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The aforementioned command makes sure that popd remains silent (do not produce any output). Similarly, you can silent pushd as well.
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The pushd and popd command are also used by Linux server administrators, who usually move around between a handful of same directories all the time. Some other really informative use-cases are explained [here][5].
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### Conclusion
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Agreed, the concept of pushd and popd isn't very straight forward. But, all it requires is a bit of practice - yes, you need to get your hands dirty. Spend some time with these commands and you'll start liking them, especially if there's a use-case where-in they make life easy for you.
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--------------------------------------------------------------------------------
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via: https://www.howtoforge.com/tutorial/linux-command-line-tips-tricks-part-2/
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作者：[Ansh ][a]
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译者：[译者ID](https://github.com/译者ID)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
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[a]:https://www.howtoforge.com/tutorial/linux-command-line-tips-tricks-part-2/
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[1]:https://www.howtoforge.com/tutorial/linux-command-line-tips-tricks-part-2/#the-basics-of-pushd-and-popd-commands
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[2]:https://www.howtoforge.com/tutorial/linux-command-line-tips-tricks-part-2/#some-advanced-points
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[3]:https://www.howtoforge.com/tutorial/linux-command-line-tips-tricks-part-2/#conclusion
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[4]:https://www.howtoforge.com/tutorial/linux-command-line-navigation-tips-and-tricks-part-1/
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[5]:http://unix.stackexchange.com/questions/77077/how-do-i-use-pushd-and-popd-commands
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Linux 命令行导航贴士：pushd 和 popd 命令基础
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============================================================
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### 在本篇中
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1. [pushd 和 popd 命令基础][1]
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2. [一些高级用法][2]
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3. [总结][3]
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在本系列的[第一部分][4]中，我们通过讨论 **cd -** 命令的用法，重点介绍了 Linux 中的命令行导航。还讨论了一些其他相关要点/概念。现在进一步讨论，在本文中，我们将讨论如何使用 pushd 和 popd 命令在 Linux 命令行上获得更快的导航体验。
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在我们开始之前，值得分享的一点是，此后提到的所有指导和命令已经在 Ubuntu 14.04 和 Bash shell（4.3.11）上测试过。
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### pushd 和 popd 命令基础
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为了更好地理解 pushd 和 popd 命令的作用，让我们先讨论堆栈的概念。想象一下你厨房案板上的一个空白区域，现在想象一下你想在上面放一套盘子。你会怎么做？很简单，一个接一个地放在上面。
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所以在整个过程的最后，案板上的第一个盘子是盘子中的最后一个，你手中最后一个盘子是盘子堆中的第一个。现在当你需要一个盘子时，你选择在堆的顶部使用它，然后在下次需要时选择下一个。
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pushd 和 popd 命令是类似的概念。在Linux系统上有一个目录堆栈，你可以堆叠目录路径以供将来使用。你可以使用 **dirs** 命令来在任何时间点快速查看堆栈的内容。
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下面的例子显示了在命令行终端启动后立即在我的系统上使用 dirs 命令的输出：
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$ dirs
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~
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输出中的波浪号（〜）表示目录堆栈当前仅包含用户的主目录。
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继续下去，使用 pushd 和 popd 命令来执行存储目录路径并删除它的操作。使用 pushd 非常容易 - 只需将要存储在目录堆栈中的路径作为此命令的参数传递。这里有一个例子：
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pushd /home/himanshu/Downloads/
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上述命令的作用是，将当前工作目录更改为你作为参数传递的目录，并且还将路径添加到目录堆栈中。为了方便用户，pushd 命令在其输出中产生目录堆栈的内容。因此，当运行上面的命令时，产生了以下输出：
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```
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~/Downloads ~
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```
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输出显示现在堆栈中有两个目录路径：一个是用户的主目录，还有用户的下载目录。它们的保存顺序是：主目录位于底部，新添加的 Downloads 目录位于其上。
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要验证 pushd 的输出是正确的，你还可以使用dirs命令：
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$ dirs
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~/Downloads ~
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因此你可以看到 dirs 命令同样产生相同的输出。
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让我们再使用下 pushd 命令：
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$ pushd /usr/lib/; pushd /home/himanshu/Desktop/
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/usr/lib ~/Downloads ~
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~/Desktop /usr/lib ~/Downloads ~
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所以目录堆栈现在包含总共四个目录路径，其中主目录（〜）在底部，并且用户的桌面目录在顶部。
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一定要记住的是堆栈的头是你当前的目录。这意味着现在我们当前的工作目录是 ~/Desktop。
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现在，假设你想回到 /usr/lib 目录，所以你所要做的就是执行 popd 命令：
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$ popd
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/usr/lib ~/Downloads ~
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popd 命令不仅会将当前目录切换到 /usr/lib，它还会从目录堆栈中删除 ~/Desktop，这一点可以从命令输出中看出。这样，popd 命令将允许你以相反的顺序浏览这些目录。
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### 一些高级用法
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现在我们已经讨论了 pushd 和 popd 命令的基础知识，让我们继续讨论与这些命令相关的一些其他细节。首先，这些命令还允许你操作目录堆栈。例如，假设你的目录堆栈看起来像这样：
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$ dirs
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~/Desktop /usr/lib ~ ~/Downloads
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现在，我们的要求是改变堆栈中目录路径的顺序，最上面的元素（~/Desktop）放到底部，剩下的每个都向上移动一个位置。这可以使用以下命令实现：
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pushd +1
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这里是上面的命令对目录堆栈做的：
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$ dirs
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/usr/lib ~ ~/Downloads ~/Desktop
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因此，我们看到目录堆栈中的元素顺序已经改变，并且现在和我们想要的一样。当然，你可以让目录堆栈元素移动任何次数。例如，以下命令会将它们向上移动两次：
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$ pushd +2
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~/Downloads ~/Desktop /usr/lib ~
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你也可以使用负的索引值：
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$ pushd -1
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/usr/lib ~ ~/Downloads ~/Desktop
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相似地，你可以在 popd 命令中使用此技术来从目录堆栈删除任何条目，而不用离开当前工作目录。例如，如果要使用 popd 从顶部（目前是 ~/Downloads）删除第三个条目，你可以运行以下命令：
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popd +2
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记住堆栈索引的初始值是 0，因此我们使用 2 来访问第三个条目。
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因此目录堆栈现在包含：
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$ dirs
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/usr/lib ~ ~/Desktop
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确认条目已经被移除了。
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如果由于某些原因，你发现你很难记住元素在目录堆栈中的位置以及它们的索引，你则可以对在 dirs 命令中使用 -v 选项。这里有一个例子：
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$ dirs -v
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0 /usr/lib
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1 ~
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2 ~/Desktop
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你可能已经猜到了，左边的数字是索引，接下来跟的是这个索引对应的目录路径。
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**注意**： 在 dir 中使用 -c 选项清除目录堆栈。
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现在让我们简要地讨论一下 popd 和 pushd 命令的实际用法。虽然它们第一眼看起来可能有点复杂，但是这些命令在编写 shell 脚本时会派上用场 - 你不需要记住你从哪里来; 只要执行一下 popd，你就能回到你来的目录。
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经验丰富的脚本编写者通常以以下方式使用这些命令：
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`popd >/dev/null 2>&1`
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上述命令确保 popd 保持静默（不产生任何输出）。同样，你也可以静默 pushd。
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pushd 和 popd 命令也被 Linux 服务器管理员使用，他们通常在几个相同的目录之间移动。 [这里][5]一些其他真正有信息量的案例解释。
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### 总结
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我同意 pushd 和 popd 的概念不是很直接。但是，它需要的只是一点练习 - 是的，你需要让你实践。花一些时间在这些命令上，你就会开始喜欢他们，特别是如果有一些能方便你生活的用例存在时。
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--------------------------------------------------------------------------------
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via: https://www.howtoforge.com/tutorial/linux-command-line-tips-tricks-part-2/
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作者：[Ansh ][a]
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译者：[geekpi](https://github.com/geekpi)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
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[a]:https://www.howtoforge.com/tutorial/linux-command-line-tips-tricks-part-2/
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[1]:https://www.howtoforge.com/tutorial/linux-command-line-tips-tricks-part-2/#the-basics-of-pushd-and-popd-commands
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[2]:https://www.howtoforge.com/tutorial/linux-command-line-tips-tricks-part-2/#some-advanced-points
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[3]:https://www.howtoforge.com/tutorial/linux-command-line-tips-tricks-part-2/#conclusion
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[4]:https://www.howtoforge.com/tutorial/linux-command-line-navigation-tips-and-tricks-part-1/
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[5]:http://unix.stackexchange.com/questions/77077/how-do-i-use-pushd-and-popd-commands
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