Merge pull request #29683 from lkxed/20230710-1-Bash-Basics-Series-5-Using-Arrays-in-Bash

[手动选题][tech]: 20230710.1 ⭐️ Bash Basics Series 5 Using Arrays in Bash.md

sources/tech/20230710.1 ⭐️ Bash Basics Series 5 Using Arrays in Bash.md

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+[#]: subject: "Bash Basics Series #5: Using Arrays in Bash"
+[#]: via: "https://itsfoss.com/bash-arrays/"
+[#]: author: "Abhishek Prakash https://itsfoss.com/author/abhishek/"
+[#]: collector: "lkxed"
+[#]: translator: " "
+[#]: reviewer: " "
+[#]: publisher: " "
+[#]: url: " "
+
+Bash Basics Series #5: Using Arrays in Bash
+======
+
+In the earlier part of the series, you learned about variables. The variables can have a single value in it.
+
+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.
+
+So, instead of declaring five variables like this:
+
+```
+distro1=Ubuntu
+distro2=Fedora
+distro3=SUSE
+distro4=Arch Linux
+distro5=Nix
+```
+
+You can initialize all of them in a single array:
+
+```
+distros=(Ubuntu Fedora SUSE "Arch Linux" Nix)
+```
+
+Unlike some other programming languages, you don't use commas as array element separators.
+
+That's good. Let's see how to access the array elements.
+
+### Accessing array elements in bash
+
+The array elements are accessed using the index (position in the array). To access array element at index N, use:
+
+```
+${array_name[N]}
+```
+
+> 💡 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`.
+
+So, if you want to print the SUSE, you'll use:
+
+```
+echo ${distros[2]}
+```
+
+![Example of accessing array elements in bash shell][1]
+
+> 🚧 There must not be any white space after `${` or before `}`. You CANNOT use it like `${ array[n] }`.
+
+### Access all array elements at once
+
+Let's say you want to print all the elements of an array.
+
+You may use echo `${array[n]}` one by one but that's really not necessary. There is a better and easier way:
+
+```
+${array[*]}
+```
+
+That will give you all the array elements.
+
+![Accessing all array elements at once in bash shell][2]
+
+### Get array length in bash
+
+How do you know how many elements are there in an array? There is a dedicated way to [get array length in Bash][3]:
+
+```
+${#array_name[@]}
+```
+
+That's so simple, right?
+
+![Get array length in bash][4]
+
+### Add array elements in bash
+
+If you have to add additional elements to an array, use the `+=` operator to [append element to existing array in bash][5]:
+
+```
+array_name+=("new_value")
+```
+
+Here's an example:
+
+![Append new element to array][6]
+
+> 🚧 It is important to use `()` while appending an element.
+
+You can also use the index to set the element at any position.
+
+```
+array_name[N]=new_value
+```
+
+**But remember to use the correct index number.** If you use it on an existing index, the new value will replace the element.
+
+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).
+
+![][7]
+
+### Delete an array element
+
+You can use `unset` shell built-in to remove an array element by providing the index number:
+
+```
+unset array_name[N]
+```
+
+Here's an example, where I delete the 4th element of the array.
+
+![Delete array element in bash][8]
+
+You can also delete the entire array with unset:
+
+```
+unset array_name
+```
+
+> 💡 There are no strict data type rules in Bash. You can create an array that contains integers and strings both.
+
+### 🏋️ Exercise time
+
+Let's practice what you learned about bash arrays.
+
+**Exercise 1**: Create a bash script that has an array of five best Linux distros. Print them all.
+
+Now, replace the middle choice with Hannah Montanna Linux.
+
+**Exercise 2**: Create a bash script that accepts three numbers from the user and then prints them in reverse order.
+
+Expected output:
+
+```
+Enter three numbers and press enter
+12 23 44
+Numbers in reverse order are: 44 23 12
+```
+
+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.
+
+--------------------------------------------------------------------------------
+
+via: https://itsfoss.com/bash-arrays/
+
+作者：[Abhishek Prakash][a]
+选题：[lkxed][b]
+译者：[译者ID](https://github.com/译者ID)
+校对：[校对者ID](https://github.com/校对者ID)
+
+本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
+
+[a]: https://itsfoss.com/author/abhishek/
+[b]: https://github.com/lkxed/
+[1]: https://itsfoss.com/content/images/2023/07/accessing-array-elements-bash.png
+[2]: https://itsfoss.com/content/images/2023/07/accessing-all-array-elements-bash.png
+[3]: https://linuxhandbook.com:443/array-length-bash/
+[4]: https://itsfoss.com/content/images/2023/07/get-array-length-bash.png
+[5]: https://linuxhandbook.com:443/bash-append-array/
+[6]: https://itsfoss.com/content/images/2023/07/append-element-to-array.png
+[7]: https://itsfoss.com/content/images/2023/07/add-array-element-bash-1.png
+[8]: https://itsfoss.com/content/images/2023/07/delete-array-element-bash.png