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geekpi
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[#]: subject: "Bash Basics Series #6: Handling String Operations"
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[#]: via: "https://itsfoss.com/bash-strings/"
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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 #6: Handling String Operations
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======
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In most programming languages, you'll find a string data type. A string is basically a group of characters.
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Bash shell is different though. There is no separate data type for strings. Everything is a variable here.
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But that doesn't mean that you cannot deal with strings in the same way you do in C and other programming languages.
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Finding substrings, replacing substrings, joining strings and many more string operations are possible in Bash shell.
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In this part of the Bash Basics Series, you'll learn the basic string manipulations.
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### Get string length in bash
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Let's start with the simplest option. Which is to get the length of a string. It's quite simple:
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```
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${#string}
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```
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Let's use it in an example.
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![Example of getting string length in bash][1]
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As you can see, the second example had two words in it but since it was in quotes, it was treated as a single word. Even the space is counted as a character.
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### Join strings in bash
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The technical term is concatenation of strings, one of the simplest possible string operations in bash.
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You just have to use the string variables one after another like this:
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```
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str3=$str1$str2
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```
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Can it go any simpler than this? I don't think so.
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Let's see it with an example. Here is my example script named `join.sh`:
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```
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#!/bin/bash
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read -p "Enter first string: " str1
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read -p "Enter second string: " str2
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joined=$str1$str2
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echo "The joined string is: $joined"
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```
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Here's a sample run of this script:
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![Join two strings in bash][2]
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### Extract substring in bash
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Let's say you have a big string with several characters and you want to extract part of it.
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To extract a substring, you need to specify the main string, the starting position of the substring and the length of the substring in the following manner:
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```
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${string:$pos:$len}
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```
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> 💡Like arrays, positioning in strings also start at 0.
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Here's an example:
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![Extracting substring in bash][3]
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Even if you specify the substring length greater than the string length, it will only go till the end of the string.
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### Replace substring in bash
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Let's say you have a big string and you want to replace part of it with another string.
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In that case, you use this kind of syntax:
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```
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${string/substr1/substr2}
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```
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> ✋ Only the first occurrence of a substring is replaced this way. If you want to replace all occurrences, use`${string//substr1/substr2}`
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Here's an example:
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![Replace substring in bash][4]
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As you can see above, the word good was replaced with best. I saved the replaced string to the same string to change the original.
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> 💡 If the substring is not found, nothing is replaced. It won't result in an error.
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### Delete substring in bash
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Let's talk about removing substrings. Let's say you want to remove part of a string. In that case, just provide the substring to the main string like this:
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```
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${string/substring}
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```
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> ✋ Only the first occurrence of a substring is deleted this way. If you want to delete all occurrences, use`${string//substr}`
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If the substring is found, it will be deleted from the string.
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Let's see this with an example.
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![Delete substring in bash][5]
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This goes without saying that if the substring is not found, it is not deleted. It won't result in an error.
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### 🏋️ Exercise time
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It's time for you to practice string manipulation with simple exercises.
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**Exercise 1**: Declare a string 'I am all wet'. Now change this string by replacing the word wet with set.
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**Exercise 2**: Create a string that saves phone numbers in the following format `112-123-1234`. Now, you have to delete all `-`.
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That should give you some decent practice with strings in bash. In the next chapter, you'll learn about using if-else statements in bash. Stay tuned.
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--------------------------------------------------------------------------------
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via: https://itsfoss.com/bash-strings/
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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/bash-string-length-example.png
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[2]: https://itsfoss.com/content/images/2023/07/join-strings-bash.png
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[3]: https://itsfoss.com/content/images/2023/07/extract-substring-bash.png
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[4]: https://itsfoss.com/content/images/2023/07/replace-substring-bash.png
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[5]: https://itsfoss.com/content/images/2023/07/bash-delete-substring.png
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@ -0,0 +1,149 @@
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[#]: subject: "Bash Basics Series #6: Handling String Operations"
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[#]: via: "https://itsfoss.com/bash-strings/"
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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 #6：处理字符串操作
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======
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在大多数编程语言中，你都会找到字符串数据类型。字符串基本上是一组字符。
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但 Bash shell 有所不同。字符串没有单独的数据类型。这里一切都是变量。
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但这并不意味着你不能像在 C 和其他编程语言中那样处理字符串。
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在 Bash shell 中可以查找子字符串、替换子字符串、连接字符串以及更多字符串操作。
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在 Bash 基础知识系列的这一部分中，你将学习基本的字符串操作。
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### 在 bash 中获取字符串长度
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让我们从最简单的选项开始。也就是获取字符串的长度。这很简单：
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```
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${#string}
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```
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让我们在示例中使用它。
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![Example of getting string length in bash][1]
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正如你所看到的，第二个示例中有两个单词，但由于它用引号引起来，因此它被视为单个单词。连空格都算作一个字符。
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### 在 bash 中连接字符串
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]
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技术术语是字符串连接，这是 bash 中最简单的字符串操作之一。
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你只需像这样一个接一个地使用字符串变量：
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```
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str3=$str1$str2
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```
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还能比这更简单吗？ 我不这么认为。
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让我们看一个例子。这是我的示例脚本，名为 `join.sh`：
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```
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#!/bin/bash
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read -p "Enter first string: " str1
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read -p "Enter second string: " str2
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joined=$str1$str2
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echo "The joined string is: $joined"
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```
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以下是该脚本的运行示例：
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![Join two strings in bash][2]
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### 在 bash 中提取子字符串
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假设你有一个包含多个字符的大字符串，并且你想要提取其中的一部分。
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要提取子字符串，需要指定主字符串、子字符串的起始位置和子字符串的长度，如下所示：
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```
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${string:$pos:$len}
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```
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> 💡和数组一样，字符串中的定位也是从 0 开始。
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这是一个例子：
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![Extracting substring in bash][3]
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即使你指定的子字符串长度大于字符串长度，它也只会到达字符串末尾。
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### 替换 bash 中的子字符串
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假设你有一个大字符串，并且你想用另一个字符串替换其中的一部分。
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在这种情况下，你可以使用这种语法：
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```
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${string/substr1/substr2}
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```
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> ✋ 只有第一次出现的子字符串才会以这种方式替换。如果要替换所有出现的地方，请使用`${string//substr1/substr2}`
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这是一个例子：
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![Replace substring in bash][4]
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正如你在上面看到的，“good” 一词被替换为 “best”。我将替换的字符串保存到同一字符串中以更改原始字符串。
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> 💡 如果未找到子字符串，则不会替换任何内容。它不会导致错误。
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### 在 bash 中删除子字符串
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我们来谈谈删除子字符串。假设你要删除字符串的一部分。在这种情况下，只需将子字符串提供给主字符串，如下所示：
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```
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${string/substring}
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```
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> ✋ 通过这种方式，仅删除第一次出现的子字符串。如果要删除所有出现的内容，请使用 `${string//substr}`
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如果找到子字符串，则将从字符串中删除它。
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让我们通过一个例子来看看。
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![Delete substring in bash][5]
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不用说，如果没有找到子字符串，则不会删除它。它不会导致错误。
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### 🏋️ 练习时间
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现在是你通过简单练习来实践字符串操作的时候了。
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**练习 1**：声明一个字符串 “I am all wet”。现在通过用 set 替换单词 wet 来更改此字符串。
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**练习 2**：创建一个字符串，以 `112-123-1234` 格式保存电话号码。现在，你必须删除所有 `-`。
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这应该会给你一些在 bash 中使用字符串的不错的练习。在下一章中，你将学习如何在 bash 中使用 if-else 语句。敬请关注。
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--------------------------------------------------------------------------------
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via: https://itsfoss.com/bash-strings/
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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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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/bash-string-length-example.png
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[2]: https://itsfoss.com/content/images/2023/07/join-strings-bash.png
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[3]: https://itsfoss.com/content/images/2023/07/extract-substring-bash.png
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[4]: https://itsfoss.com/content/images/2023/07/replace-substring-bash.png
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[5]: https://itsfoss.com/content/images/2023/07/bash-delete-substring.png
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