bash 'cd $_' 是什么意思？
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/30154694/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
what does 'cd $_' mean?
提问by Mukund Kumar
I have seen this command in a tutorial to create a new directory:
我在创建新目录的教程中看到了这个命令：
mkdir my-new-project && cd $_
I know mkdir my-new-projectcommand is used to create a new directory, but what does cd $_do?
我知道mkdir my-new-projectcommand 用于创建一个新目录，但是有什么作用cd $_呢？
回答by PSkocik
$_expands to the last argument to the previous simple command*or to previous command if it had no arguments.
$_扩展到上一个简单命令*的最后一个参数，如果没有参数则扩展到上一个命令。
mkdir my-new-project && cd $_
^ Here you have a command made of two simple commands. The last argument to the first one is my-new-projectso $_in the second simple commandwill expand to my-new-project.
^ 这里有一个由两个简单命令组成的命令。的最后一个参数，第一个是my-new-project因此$_在第二简单的命令将扩大到my-new-project。
To give another example:
再举一个例子：
echo a b; echo $_
#Will output:
#a b
#b
In any case, mkdir some_dir && cd $_is a very common combo. If you get tired of typing it, I think it's a good idea to make it a function:
无论如何，mkdir some_dir && cd $_是一个很常见的组合。如果你厌倦了打字，我认为把它变成一个函数是个好主意：
mkdircd() {
#Make path for each argument and cd into the last path
mkdir -p "$@" && cd "$_"
}
*
The bash manualdefines a simple commandas "a sequence of optional variable assignments followed by blank-separated words and redirections, and terminated by a control operator."where control operatorrefers to one of || & && ; ;; ( ) | |& <newline>.
* bash 手册将一个简单的命令定义为“一系列可选的变量赋值，后跟空格分隔的单词和重定向，并由控制运算符终止。”其中控制运算符指的是|| & && ; ;; ( ) | |& <newline>.
In practice$_works like I've described but only with ||, &&, ;, or newlineas the control operator.
在实际应用中$_的作品像我描述，但只能用||，&&，;或换行的控制操作。
回答by Kaotikus
7. How to create directory and switch to it using single command. As you might already know, the && operator is used for executing multiple commands, and $_ expands to the last argument of the previous command.
7. 如何创建目录并使用单个命令切换到该目录。您可能已经知道，&& 运算符用于执行多个命令，而 $_ 扩展为前一个命令的最后一个参数。
Quickly, if you want, you can create a directory and also move to that directory by using a single command. To do this, run the following command:
很快，如果需要，您可以创建一个目录并使用单个命令移动到该目录。为此，请运行以下命令：
$ mkdir [dir-name] && cd $_
For those coming from Udacity's Version Control with Git, HowToForge offers a great explanation, here.
对于那些来自 Udacity 的 Git 版本控制的人，HowToForge 提供了一个很好的解释，这里。
