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[#]: subject: "Bash Basics Series #5: Using Arrays in Bash"
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[#]: via: "https://itsfoss.com/bash-arrays/"
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[#]: author: "Abhishek Prakash https://itsfoss.com/author/abhishek/"
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[#]: collector: "lkxed"
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[#]: translator: "geekpi"
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[#]: reviewer: " "
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[#]: publisher: " "
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[#]: url: " "
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Bash Basics Series #5: Using Arrays in Bash
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======
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In the earlier part of the series, you learned about variables. The variables can have a single value in it.
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Arrays can have several values inside it. This makes things easier when you have to deal with several variables at a time. You don't have to store individual values in a new variable.
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So, instead of declaring five variables like this:
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```
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distro1=Ubuntu
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distro2=Fedora
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distro3=SUSE
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distro4=Arch Linux
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distro5=Nix
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```
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You can initialize all of them in a single array:
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```
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distros=(Ubuntu Fedora SUSE "Arch Linux" Nix)
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```
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Unlike some other programming languages, you don't use commas as array element separators.
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That's good. Let's see how to access the array elements.
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### Accessing array elements in bash
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The array elements are accessed using the index (position in the array). To access array element at index N, use:
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```
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${array_name[N]}
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```
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> 💡 Like most other programming languages, the array starts at index 0 in Bash shell. This means the first element has index 0, the second element has index 1 and the `nth` element has index `n-1`.
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So, if you want to print the SUSE, you'll use:
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```
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echo ${distros[2]}
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```
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![Example of accessing array elements in bash shell][1]
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> 🚧 There must not be any white space after `${` or before `}`. You CANNOT use it like `${ array[n] }`.
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### Access all array elements at once
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Let's say you want to print all the elements of an array.
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You may use echo `${array[n]}` one by one but that's really not necessary. There is a better and easier way:
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```
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${array[*]}
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```
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That will give you all the array elements.
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![Accessing all array elements at once in bash shell][2]
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### Get array length in bash
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How do you know how many elements are there in an array? There is a dedicated way to [get array length in Bash][3]:
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```
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${#array_name[@]}
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```
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That's so simple, right?
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![Get array length in bash][4]
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### Add array elements in bash
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If you have to add additional elements to an array, use the `+=` operator to [append element to existing array in bash][5]:
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```
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array_name+=("new_value")
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```
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Here's an example:
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![Append new element to array][6]
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> 🚧 It is important to use `()` while appending an element.
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You can also use the index to set the element at any position.
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```
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array_name[N]=new_value
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```
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**But remember to use the correct index number.** If you use it on an existing index, the new value will replace the element.
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If you use an 'out of bound' index, it will still be added after the last element. For example, if the array length is six and you try to set a new value at index 9, it will still be added as the last element at the 7th position (index 6).
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![][7]
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### Delete an array element
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You can use `unset` shell built-in to remove an array element by providing the index number:
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```
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unset array_name[N]
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```
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Here's an example, where I delete the 4th element of the array.
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![Delete array element in bash][8]
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You can also delete the entire array with unset:
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```
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unset array_name
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```
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> 💡 There are no strict data type rules in Bash. You can create an array that contains integers and strings both.
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### 🏋️ Exercise time
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Let's practice what you learned about bash arrays.
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**Exercise 1**: Create a bash script that has an array of five best Linux distros. Print them all.
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Now, replace the middle choice with Hannah Montanna Linux.
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**Exercise 2**: Create a bash script that accepts three numbers from the user and then prints them in reverse order.
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Expected output:
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```
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Enter three numbers and press enter
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12 23 44
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Numbers in reverse order are: 44 23 12
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```
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I hope you are enjoying learning bash shell scripting with this series. In the next chapter, you'll learn about using if-else. Stay tuned.
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--------------------------------------------------------------------------------
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via: https://itsfoss.com/bash-arrays/
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作者：[Abhishek Prakash][a]
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选题：[lkxed][b]
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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://itsfoss.com/author/abhishek/
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[b]: https://github.com/lkxed/
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[1]: https://itsfoss.com/content/images/2023/07/accessing-array-elements-bash.png
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[2]: https://itsfoss.com/content/images/2023/07/accessing-all-array-elements-bash.png
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[3]: https://linuxhandbook.com:443/array-length-bash/
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[4]: https://itsfoss.com/content/images/2023/07/get-array-length-bash.png
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[5]: https://linuxhandbook.com:443/bash-append-array/
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[6]: https://itsfoss.com/content/images/2023/07/append-element-to-array.png
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[7]: https://itsfoss.com/content/images/2023/07/add-array-element-bash-1.png
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[8]: https://itsfoss.com/content/images/2023/07/delete-array-element-bash.png
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@ -0,0 +1,169 @@
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[#]: subject: "Bash Basics Series #5: Using Arrays in Bash"
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[#]: via: "https://itsfoss.com/bash-arrays/"
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[#]: author: "Abhishek Prakash https://itsfoss.com/author/abhishek/"
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[#]: collector: "lkxed"
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[#]: translator: "geekpi"
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[#]: reviewer: " "
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[#]: publisher: " "
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[#]: url: " "
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Bash 基础知识系列 #5：在 Bash 中使用数组
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======
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在本系列的前面部分中，你了解了变量。变量中可以有单个值。
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数组内部可以有多个值。当你必须一次处理多个变量时，这会使事情变得更容易。你不必将各个值存储在新变量中。
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因此，不要像这样声明五个变量：
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```
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distro1=Ubuntu
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distro2=Fedora
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distro3=SUSE
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distro4=Arch Linux
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distro5=Nix
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```
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你可以在单个数组中初始化它们所有：
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```
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distros=(Ubuntu Fedora SUSE "Arch Linux" Nix)
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```
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与其他一些编程语言不同，你不使用逗号作为数组元素分隔符。
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那挺好的。让我们看看如何访问数组元素。
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### 在 bash 中访问数组元素
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使用索引（数组中的位置）访问数组元素。要访问索引 N 处的数组元素，请使用：
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```
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${array_name[N]}
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```
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> 💡 与大多数其他编程语言一样，Bash shell 中的数组从索引 0 开始。这意味着第一个元素的索引为 0，第二个元素的索引为 1，`第 n 个`元素的索引为 `n-1`。
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因此，如果你想打印 SUSE，你将使用：
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```
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echo ${distros[2]}
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```
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![Example of accessing array elements in bash shell][1]
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> 🚧 `${` 之后或 `}` 之前不能有任何空格。你不能像 `${ array[n] }` 那样使用它。
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### 一次访问所有数组元素
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假设你要打印数组的所有元素。
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你可以一一使用 echo `${array[n]}` 但这确实没有必要。有一个更好更简单的方法：
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```
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${array[*]}
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```
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这将为你提供所有数组元素。
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![Accessing all array elements at once in bash shell][2]
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### 在 bash 中获取数组长度
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如何知道数组中有多少个元素？ 有一个专门的方法[在 Bash 中获取数组长度][3]：
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```
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${#array_name[@]}
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```
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就这么简单，对吧？
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![Get array length in bash][4]
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### 在 bash 中添加数组元素
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如果必须向数组添加其他元素，请使用 `+=` 运算符[将元素追加到 bash 中的现有数组][5]：
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```
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array_name+=("new_value")
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```
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这是一个例子：
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![Append new element to array][6]
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> 🚧 追加元素时使用 `()` 很重要。
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你还可以使用索引将元素设置在任何位置。
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```
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array_name[N]=new_value
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```
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**但请记住使用正确的索引编号。** 如果在现有索引上使用它，新值将替换该元素。
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如果你使用“越界”索引，它仍会添加到最后一个元素之后。例如，如果数组长度为 6，并且你尝试在索引 9 处设置新值，则该值仍将作为最后一个元素添加到第 7 个位置（索引 6）。
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![][7]
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### 删除数组元素
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你可以使用内置的 `unset` shell 通过提供索引号来删除数组元素：
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```
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unset array_name[N]
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```
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这是一个示例，我删除了数组的第四个元素。
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![Delete array element in bash][8]
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你还可以通过 unset 来删除整个数组：
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```
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unset array_name
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```
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> 💡 Bash 中没有严格的数据类型规则。你可以创建一个同时包含整数和字符串的数组。
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### 🏋️ 练习时间
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让我们练习一下你所学到的有关 bash 数组的知识。
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**练习 1**：创建一个 bash 脚本，其中包含五个最佳 Linux 发行版的数组。全部打印出来。
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现在，用 Hannah Montanna Linux 替换中间的选择。
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**练习 2**：创建一个 bash 脚本，该脚本接受用户提供的三个数字，然后以相反的顺序打印它们。
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预期输出：
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```
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Enter three numbers and press enter
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12 23 44
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Numbers in reverse order are: 44 23 12
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```
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我希望你喜欢通过本系列学习 bash shell 脚本。在下一章中，你将学习如何使用 if-else。敬请关注。
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--------------------------------------------------------------------------------
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via: https://itsfoss.com/bash-arrays/
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作者：[Abhishek Prakash][a]
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选题：[lkxed][b]
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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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||||
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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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||||
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||||
[a]: https://itsfoss.com/author/abhishek/
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[b]: https://github.com/lkxed/
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[1]: https://itsfoss.com/content/images/2023/07/accessing-array-elements-bash.png
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[2]: https://itsfoss.com/content/images/2023/07/accessing-all-array-elements-bash.png
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[3]: https://linuxhandbook.com:443/array-length-bash/
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[4]: https://itsfoss.com/content/images/2023/07/get-array-length-bash.png
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[5]: https://linuxhandbook.com:443/bash-append-array/
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[6]: https://itsfoss.com/content/images/2023/07/append-element-to-array.png
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[7]: https://itsfoss.com/content/images/2023/07/add-array-element-bash-1.png
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[8]: https://itsfoss.com/content/images/2023/07/delete-array-element-bash.png
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