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Merge remote-tracking branch 'LCTT/master'
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Xingyu Wang
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41fe2b3fb8
@ -1,8 +1,8 @@
|
||||
[#]: collector: (lujun9972)
|
||||
[#]: translator: (gxlct008)
|
||||
[#]: reviewer: ( )
|
||||
[#]: publisher: ( )
|
||||
[#]: url: ( )
|
||||
[#]: reviewer: (wxy)
|
||||
[#]: publisher: (wxy)
|
||||
[#]: url: (https://linux.cn/article-12693-1.html)
|
||||
[#]: subject: (Create a mobile app with Flutter)
|
||||
[#]: via: (https://opensource.com/article/20/9/mobile-app-flutter)
|
||||
[#]: author: (Vitaly Kuprenko https://opensource.com/users/kooper)
|
||||
@ -10,14 +10,15 @@
|
||||
使用 Flutter 创建 App
|
||||
======
|
||||
|
||||
使用流行的 Flutter 框架开始您的跨平台开发之旅。
|
||||
![A person looking at a phone][1]
|
||||
> 使用流行的 Flutter 框架开始你的跨平台开发之旅。
|
||||
|
||||
[Flutter][2] 是一个深受全球移动开发者欢迎的项目。该框架有一个庞大的、友好的发烧友社区，随着 Flutter 帮助程序员将他们的项目带入移动领域，这个社区还在继续增长。
|
||||
|
||||
|
||||
本教程旨在帮助您开始使用 Flutter 进行移动开发。阅读之后，您将了解如何快速安装和设置框架，以便开始为智能手机、平板电脑和其他平台编码。
|
||||
[Flutter][2] 是一个深受全球移动开发者欢迎的项目。该框架有一个庞大的、友好的爱好者社区，随着 Flutter 帮助程序员将他们的项目带入移动领域，这个社区还在继续增长。
|
||||
|
||||
本操作指南假定您已在计算机上安装了 [Android Studio][3]，并且具有一定的使用经验。
|
||||
本教程旨在帮助你开始使用 Flutter 进行移动开发。阅读之后，你将了解如何快速安装和设置框架，以便开始为智能手机、平板电脑和其他平台开发。
|
||||
|
||||
本操作指南假定你已在计算机上安装了 [Android Studio][3]，并且具有一定的使用经验。
|
||||
|
||||
### 什么是 Flutter ？
|
||||
|
||||
@ -25,15 +26,15 @@ Flutter 使得开发人员能够为多个平台构建应用程序，包括：
|
||||
|
||||
* Android
|
||||
* iOS
|
||||
* Web (测试版)
|
||||
* macOS (正在开发中)
|
||||
* Linux (正在开发中)
|
||||
* Web（测试版）
|
||||
* macOS（正在开发中）
|
||||
* Linux（正在开发中）
|
||||
|
||||
对 macOS 和 Linux 的支持还处于早期开发阶段，而 Web 支持预计很快就会发布。这意味着您可以立即试用其功能（如下所述）。
|
||||
对 macOS 和 Linux 的支持还处于早期开发阶段，而 Web 支持预计很快就会发布。这意味着你可以立即试用其功能（如下所述）。
|
||||
|
||||
### 安装 Flutter
|
||||
|
||||
我使用的是 Ubuntu18.04，但安装过程与其他 Linux 发行版类似，比如 Arch 或 Mint。
|
||||
我使用的是 Ubuntu 18.04，但其他 Linux 发行版安装过程与之类似，比如 Arch 或 Mint。
|
||||
|
||||
#### 使用 snapd 安装
|
||||
|
||||
@ -46,31 +47,27 @@ $ sudo snap install flutter –classic
|
||||
flutter 0+git.142868f from flutter Team/ installed
|
||||
```
|
||||
|
||||
然后使用 `flutter` 命令启动它。 首次启动时，该框架会下载到您的计算机上：
|
||||
然后使用 `flutter` 命令启动它。 首次启动时，该框架会下载到你的计算机上：
|
||||
|
||||
```
|
||||
$ flutter
|
||||
Initializing Flutter
|
||||
Downloading <https://storage.googleapis.com/flutter\_infra\[...\]>
|
||||
Downloading https://storage.googleapis.com/flutter_infra[...]
|
||||
```
|
||||
|
||||
下载完成后，您会看到一条消息，告诉您 Flutter 已初始化：
|
||||
下载完成后，你会看到一条消息，告诉你 Flutter 已初始化：
|
||||
|
||||
![Flutter initialized][5]
|
||||
|
||||
(Vitaly Kuprenko, [CC BY-SA 4.0][6])
|
||||
|
||||
#### 手动安装
|
||||
|
||||
如果您没有安装 Snapd，或者您的发行版不是 Ubuntu，那么安装过程会略有不同。 在这种情况下，请[下载] [7] 为您的操作系统推荐的 Flutter 版本。
|
||||
如果你没有安装 Snapd，或者你的发行版不是 Ubuntu，那么安装过程会略有不同。在这种情况下，请[下载][7] 为你的操作系统推荐的 Flutter 版本。
|
||||
|
||||
![Install Flutter manually][8]
|
||||
|
||||
(Vitaly Kuprenko, [CC BY-SA 4.0][6])
|
||||
然后将其解压缩到你的主目录。
|
||||
|
||||
然后将其解压缩到您的主目录。
|
||||
|
||||
在您喜欢的文本编辑器中打开主目录中的 `.bashrc` 文件 (如果您使用 [Z shell][9]，则打开 `.zshc`)。因为它是隐藏文件，所以您必须首先在文件管理器中启用显示隐藏文件，或者使用以下命令从终端打开它：
|
||||
在你喜欢的文本编辑器中打开主目录中的 `.bashrc` 文件（如果你使用 [Z shell][9]，则打开 `.zshc`）。因为它是隐藏文件，所以你必须首先在文件管理器中启用显示隐藏文件，或者使用以下命令从终端打开它：
|
||||
|
||||
```
|
||||
$ gedit ~/.bashrc &
|
||||
@ -82,48 +79,43 @@ $ gedit ~/.bashrc &
|
||||
export PATH="$PATH:~/flutter/bin"
|
||||
```
|
||||
|
||||
保存并关闭文件。 请记住，如果将 Flutter 提取到您的主目录之外的其他位置，则 [Flutter SDK 的路径][10] 将有所不同。
|
||||
保存并关闭文件。 请记住，如果在你的主目录之外的其他位置解压 Flutter，则 [Flutter SDK 的路径][10] 将有所不同。
|
||||
|
||||
关闭您的终端，然后再次打开，以便加载新配置。 或者，您可以通过以下命令使配置立即生效：
|
||||
关闭你的终端，然后再次打开，以便加载新配置。 或者，你可以通过以下命令使配置立即生效：
|
||||
|
||||
```
|
||||
$ . ~/.bashrc
|
||||
```
|
||||
|
||||
如果您没有看到错误，那说明一切都是正常的。
|
||||
|
||||
这种安装方法比使用 `snap`命令稍微困难一些，但是它非常通用，可以让您在几乎所有的发行版上安装框架。
|
||||
如果你没有看到错误，那说明一切都是正常的。
|
||||
|
||||
这种安装方法比使用 `snap` 命令稍微困难一些，但是它非常通用，可以让你在几乎所有的发行版上安装该框架。
|
||||
|
||||
#### 检查安装结果
|
||||
|
||||
要检查结果，请在终端中输入以下内容：
|
||||
要检查安装结果，请在终端中输入以下内容：
|
||||
|
||||
```
|
||||
flutter doctor -v
|
||||
```
|
||||
|
||||
您将看到有关已安装组件的信息。 如果看到错误，请不要担心。 您尚未安装任何用于 Flutter SDK 的 IDE 插件。
|
||||
你将看到有关已安装组件的信息。 如果看到错误，请不要担心。 你尚未安装任何用于 Flutter SDK 的 IDE 插件。
|
||||
|
||||
![Checking Flutter installation with the doctor command][11]
|
||||
|
||||
(Vitaly Kuprenko, [CC BY-SA 4.0][6])
|
||||
|
||||
### 安装 IDE 插件
|
||||
|
||||
您应该在您的 [集成开发环境 (IDE)][12] 中安装插件，以帮助它与 Flutter SDK 接口、与设备交互并构建代码。
|
||||
你应该在你的 [集成开发环境（IDE）][12] 中安装插件，以帮助它与 Flutter SDK 接口、与设备交互并构建代码。
|
||||
|
||||
Flutter 开发中常用的三个主要 IDE 工具是 IntelliJ IDEA (社区版)、Android Studio 和 VS Code (或 [VSCodium][13])。我在本教程中使用的是 Android Studio，但步骤与它们在 IntelliJ Idea (社区版)上的工作方式相似，因为它们构建在相同的平台上。
|
||||
Flutter 开发中常用的三个主要 IDE 工具是 IntelliJ IDEA（社区版）、Android Studio 和 VS Code（或 [VSCodium][13]）。我在本教程中使用的是 Android Studio，但步骤与它们在 IntelliJ Idea（社区版）上的工作方式相似，因为它们构建在相同的平台上。
|
||||
|
||||
首先，启动 **Android Studio**。打开 **Settings**，进入 **Plugins** 窗格，选择 **Marketplace** 选项卡。在搜索行中输入 **Flutter**，然后单击 **Install**。
|
||||
首先，启动 Android Studio。打开 “Settings”，进入 “Plugins” 窗格，选择 “Marketplace” 选项卡。在搜索行中输入 “Flutter”，然后单击 “Install”。
|
||||
|
||||
![Flutter plugins][14]
|
||||
|
||||
(Vitaly Kuprenko, [CC BY-SA 4.0][6])
|
||||
你可能会看到一个安装 “Dart” 插件的选项；同意它。如果看不到 Dart 选项，请通过重复上述步骤手动安装它。我还建议使用 “Rainbow Brackets” 插件，它可以让代码导航更简单。
|
||||
|
||||
您可能会看到一个安装 **Dart** 插件的选项；同意它。如果看不到 Dart 选项，请通过重复上述步骤手动安装。我还建议使用 **Rainbow Brackets** 插件，它可以让代码导航更简单。
|
||||
|
||||
就这样！您已经安装了所需的所有插件。您可以在终端中输入一个熟悉的命令进行检查：
|
||||
就这样！你已经安装了所需的所有插件。你可以在终端中输入一个熟悉的命令进行检查：
|
||||
|
||||
```
|
||||
flutter doctor -v
|
||||
@ -131,47 +123,37 @@ flutter doctor -v
|
||||
|
||||
![Checking Flutter plugins with the doctor command][15]
|
||||
|
||||
(Vitaly Kuprenko, [CC BY-SA 4.0][6])
|
||||
|
||||
### 构建您的 “Hello World” 应用程序
|
||||
### 构建你的 “Hello World” 应用程序
|
||||
|
||||
要启动新项目，请创建一个 Flutter 项目：
|
||||
|
||||
1. 选择 **New -> New Flutter project**.
|
||||
1、选择 “New -> New Flutter project”。
|
||||
|
||||
![Creating a new Flutter plugin][16]
|
||||
|
||||
(Vitaly Kuprenko, [CC BY-SA 4.0][6])
|
||||
2、在窗口中，选择所需的项目类型。 在这种情况下，你需要选择 “Flutter Application”。
|
||||
|
||||
2. 在窗口中，选择所需的项目类型。 在这种情况下，您需要选择 **Flutter Application**。
|
||||
|
||||
3. 命名您的项目 **hello_world**。 请注意，您应该使用合并的名称，因此请使用下划线而不是空格。 您可能还需要指定 SDK 的路径。
|
||||
3、命名你的项目为 `hello_world`。 请注意，你应该使用合并的名称，因此请使用下划线而不是空格。 你可能还需要指定 SDK 的路径。
|
||||
|
||||
![Naming a new Flutter plugin][17]
|
||||
|
||||
(Vitaly Kuprenko, [CC BY-SA 4.0][6])
|
||||
4、输入软件包名称。
|
||||
|
||||
4. 输入软件包名称。
|
||||
|
||||
您已经创建了一个项目！现在，您可以在设备上或使用模拟器启动它。
|
||||
你已经创建了一个项目！现在，你可以在设备上或使用模拟器启动它。
|
||||
|
||||
![Device options in Flutter][18]
|
||||
|
||||
(Vitaly Kuprenko, [CC BY-SA 4.0][6])
|
||||
|
||||
选择您想要的设备，然后按 **运行**。稍后，您将看到结果。
|
||||
选择你想要的设备，然后按 “Run”。稍后，你将看到结果。
|
||||
|
||||
![Flutter demo on mobile device][19]
|
||||
|
||||
(Vitaly Kuprenko, [CC BY-SA 4.0][6])
|
||||
|
||||
现在你可以在一个 [中间项目][20] 上开始工作了。
|
||||
|
||||
### 尝试 Flutter for web
|
||||
|
||||
在安装 Flutter 的 Web 组件之前，您应该知道 Flutter 目前对 Web 应用程序的支持还很原始。 因此，将其用于复杂的项目并不是一个好主意。
|
||||
在安装 Flutter 的 Web 组件之前，你应该知道 Flutter 目前对 Web 应用程序的支持还很原始。 因此，将其用于复杂的项目并不是一个好主意。
|
||||
|
||||
默认情况下，基本 SDK 中不启用 Flutter for web。 要打开它，请转到 beta 频道。 为此，请在终端中输入以下命令：
|
||||
默认情况下，基本 SDK 中不启用 “Flutter for web”。 要打开它，请转到 beta 通道。 为此，请在终端中输入以下命令：
|
||||
|
||||
```
|
||||
flutter channel beta
|
||||
@ -179,8 +161,6 @@ flutter channel beta
|
||||
|
||||
![flutter channel beta output][21]
|
||||
|
||||
(Vitaly Kuprenko, [CC BY-SA 4.0][6])
|
||||
|
||||
接下来，使用以下命令根据 beta 分支升级 Flutter：
|
||||
|
||||
```
|
||||
@ -189,23 +169,19 @@ flutter upgrade
|
||||
|
||||
![flutter upgrade output][22]
|
||||
|
||||
(Vitaly Kuprenko, [CC BY-SA 4.0][6])
|
||||
|
||||
要使 Flutter for web 工作，请输入：
|
||||
要使 “Flutter for web” 工作，请输入：
|
||||
|
||||
```
|
||||
flutter config --enable-web
|
||||
```
|
||||
|
||||
重新启动 IDE；这有助于 Android Studio 索引新的 IDE 并重新加载设备列表。您应该会看到几个新设备：
|
||||
重新启动 IDE；这有助于 Android Studio 索引新的 IDE 并重新加载设备列表。你应该会看到几个新设备：
|
||||
|
||||
![Flutter for web device options][23]
|
||||
|
||||
(Vitaly Kuprenko, [CC BY-SA 4.0][6])
|
||||
选择 “Chrome” 会在浏览器中启动一个应用程序， “Web Server” 会提供指向你的 Web 应用程序的链接，你可以在任何浏览器中打开它。
|
||||
|
||||
选择 **Chrome** 会在浏览器中启动一个应用程序， **Web Server** 会提供指向您的 Web 应用程序的链接，您可以在任何浏览器中打开它。
|
||||
|
||||
不过，现在还不是急于开发的时候，因为您当前的项目不支持Web。要改进它，请打开项目根目录下的终端，然后输入：
|
||||
不过，现在还不是急于开发的时候，因为你当前的项目不支持 Web。要改进它，请打开项目根目录下的终端，然后输入：
|
||||
|
||||
```
|
||||
flutter create
|
||||
@ -213,25 +189,21 @@ flutter create
|
||||
|
||||
此命令重新创建项目，并添加 Web 支持。 现有代码不会被删除。
|
||||
|
||||
请注意，目录树已更改，现在有了一个 "web" 目录：
|
||||
请注意，目录树已更改，现在有了一个 `web` 目录：
|
||||
|
||||
![File tree with web directory][24]
|
||||
|
||||
(Vitaly Kuprenko, [CC BY-SA 4.0][6])
|
||||
|
||||
现在您可以开始工作了。 选择 **Chrome**，然后按 **Run**。 稍后，您会看到带有应用程序的浏览器窗口。
|
||||
现在你可以开始工作了。 选择 “Chrome”，然后按 “Run”。 稍后，你会看到带有应用程序的浏览器窗口。
|
||||
|
||||
![Flutter web app demo][25]
|
||||
|
||||
(Vitaly Kuprenko, [CC BY-SA 4.0][6])
|
||||
|
||||
恭喜你！ 您刚刚为浏览器启动了一个项目，并且可以像其他任何网站一样继续使用它。
|
||||
恭喜你！ 你刚刚为浏览器启动了一个项目，并且可以像其他任何网站一样继续使用它。
|
||||
|
||||
所有这些都来自同一代码库，因为 Flutter 使得几乎无需更改就可以为移动平台和 Web 编写代码。
|
||||
|
||||
### 用 Flutter 做更多的事情
|
||||
|
||||
Flutter 是用于移动开发的强大工具，而且它也是迈向跨平台开发的重要一步。 了解它，使用它，并将您的应用程序交付到所有平台！
|
||||
Flutter 是用于移动开发的强大工具，而且它也是迈向跨平台开发的重要一步。 了解它，使用它，并将你的应用程序交付到所有平台！
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
@ -239,8 +211,8 @@ via: https://opensource.com/article/20/9/mobile-app-flutter
|
||||
|
||||
作者：[Vitaly Kuprenko][a]
|
||||
选题：[lujun9972][b]
|
||||
译者：[译者ID](https://github.com/gxlct008)
|
||||
校对：[校对者ID](https://github.com/校对者ID)
|
||||
译者：[gxlct008](https://github.com/gxlct008)
|
||||
校对：[wxy](https://github.com/wxy)
|
||||
|
||||
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
|
||||
|
||||
@ -1,136 +0,0 @@
|
||||
[#]: collector: (lujun9972)
|
||||
[#]: translator: (rakino)
|
||||
[#]: reviewer: ( )
|
||||
[#]: publisher: ( )
|
||||
[#]: url: ( )
|
||||
[#]: subject: (Things You Didn't Know About GNU Readline)
|
||||
[#]: via: (https://twobithistory.org/2019/08/22/readline.html)
|
||||
[#]: author: (Two-Bit History https://twobithistory.org)
|
||||
|
||||
Things You Didn't Know About GNU Readline
|
||||
======
|
||||
|
||||
I sometimes think of my computer as a very large house. I visit this house every day and know most of the rooms on the ground floor, but there are bedrooms I’ve never been in, closets I haven’t opened, nooks and crannies that I’ve never explored. I feel compelled to learn more about my computer the same way anyone would feel compelled to see a room they had never visited in their own home.
|
||||
|
||||
GNU Readline is an unassuming little software library that I relied on for years without realizing that it was there. Tens of thousands of people probably use it every day without thinking about it. If you use the Bash shell, every time you auto-complete a filename, or move the cursor around within a single line of input text, or search through the history of your previous commands, you are using GNU Readline. When you do those same things while using the command-line interface to Postgres (`psql`), say, or the Ruby REPL (`irb`), you are again using GNU Readline. Lots of software depends on the GNU Readline library to implement functionality that users expect, but the functionality is so auxiliary and unobtrusive that I imagine few people stop to wonder where it comes from.
|
||||
|
||||
GNU Readline was originally created in the 1980s by the Free Software Foundation. Today, it is an important if invisible part of everyone’s computing infrastructure, maintained by a single volunteer.
|
||||
|
||||
### Feature Replete
|
||||
|
||||
The GNU Readline library exists primarily to augment any command-line interface with a common set of keystrokes that allow you to move around within and edit a single line of input. If you press `Ctrl-A` at a Bash prompt, for example, that will jump your cursor to the very beginning of the line, while pressing `Ctrl-E` will jump it to the end. Another useful command is `Ctrl-U`, which will delete everything in the line before the cursor.
|
||||
|
||||
For an embarrassingly long time, I moved around on the command line by repeatedly tapping arrow keys. For some reason, I never imagined that there was a faster way to do it. Of course, no programmer familiar with a text editor like Vim or Emacs would deign to punch arrow keys for long, so something like Readline was bound to be created. Using Readline, you can do much more than just jump around—you can edit your single line of text as if you were using a text editor. There are commands to delete words, transpose words, upcase words, copy and paste characters, etc. In fact, most of Readline’s keystrokes/shortcuts are based on Emacs. Readline is essentially Emacs for a single line of text. You can even record and replay macros.
|
||||
|
||||
I have never used Emacs, so I find it hard to remember what all the different Readline commands are. But one thing about Readline that is really neat is that you can switch to using a Vim-based mode instead. To do this for Bash, you can use the `set` builtin. The following will tell Readline to use Vim-style commands for the current shell:
|
||||
|
||||
```
|
||||
$ set -o vi
|
||||
```
|
||||
|
||||
With this option enabled, you can delete words using `dw` and so on. The equivalent to `Ctrl-U` in the Emacs mode would be `d0`.
|
||||
|
||||
I was excited to try this when I first learned about it, but I’ve found that it doesn’t work so well for me. I’m happy that this concession to Vim users exists, and you might have more luck with it than me, particularly if you haven’t already used Readline’s default command keystrokes. My problem is that, by the time I heard about the Vim-based interface, I had already learned several Readline keystrokes. Even with the Vim option enabled, I keep using the default keystrokes by mistake. Also, without some sort of indicator, Vim’s modal design is awkward here—it’s very easy to forget which mode you’re in. So I’m stuck at a local maximum using Vim as my text editor but Emacs-style Readline commands. I suspect a lot of other people are in the same position.
|
||||
|
||||
If you feel, not unreasonably, that both Vim and Emacs’ keyboard command systems are bizarre and arcane, you can customize Readline’s key bindings and make them whatever you like. This is not hard to do. Readline reads a `~/.inputrc` file on startup that can be used to configure various options and key bindings. One thing I’ve done is reconfigured `Ctrl-K`. Normally it deletes from the cursor to the end of the line, but I rarely do that. So I’ve instead bound it so that pressing `Ctrl-K` deletes the whole line, regardless of where the cursor is. I’ve done that by adding the following to `~/.inputrc`:
|
||||
|
||||
```
|
||||
Control-k: kill-whole-line
|
||||
```
|
||||
|
||||
Each Readline command (the documentation refers to them as _functions_) has a name that you can associate with a key sequence this way. If you edit `~/.inputrc` in Vim, it turns out that Vim knows the filetype and will help you by highlighting valid function names but not invalid ones!
|
||||
|
||||
Another thing you can do with `~/.inputrc` is create canned macros by mapping key sequences to input strings. [The Readline manual][1] gives one example that I think is especially useful. I often find myself wanting to save the output of a program to a file, which means that I often append something like `> output.txt` to Bash commands. To save some time, you could make this a Readline macro:
|
||||
|
||||
```
|
||||
Control-o: "> output.txt"
|
||||
```
|
||||
|
||||
Now, whenever you press `Ctrl-O`, you’ll see that `> output.txt` gets added after your cursor on the command line. Neat!
|
||||
|
||||
But with macros you can do more than just create shortcuts for strings of text. The following entry in `~/.inputrc` means that, every time I press `Ctrl-J`, any text I already have on the line is surrounded by `$(` and `)`. The macro moves to the beginning of the line with `Ctrl-A`, adds `$(`, then moves to the end of the line with `Ctrl-E` and adds `)`:
|
||||
|
||||
```
|
||||
Control-j: "\C-a$(\C-e)"
|
||||
```
|
||||
|
||||
This might be useful if you often need the output of one command to use for another, such as in:
|
||||
|
||||
```
|
||||
$ cd $(brew --prefix)
|
||||
```
|
||||
|
||||
The `~/.inputrc` file also allows you to set different values for what the Readline manual calls _variables_. These enable or disable certain Readline behaviors. You can use these variables to change, for example, how Readline auto-completion works or how the Readline history search works. One variable I’d recommend turning on is the `revert-all-at-newline` variable, which by default is off. When the variable is off, if you pull a line from your command history using the reverse search feature, edit it, but then decide to search instead for another line, the edit you made is preserved in the history. I find this confusing because it leads to lines showing up in your Bash command history that you never actually ran. So add this to your `~/.inputrc`:
|
||||
|
||||
```
|
||||
set revert-all-at-newline on
|
||||
```
|
||||
|
||||
When you set options or key bindings using `~/.inputrc`, they apply wherever the Readline library is used. This includes Bash most obviously, but you’ll also get the benefit of your changes in other programs like `irb` and `psql` too! A Readline macro that inserts `SELECT * FROM` could be useful if you often use command-line interfaces to relational databases.
|
||||
|
||||
### Chet Ramey
|
||||
|
||||
GNU Readline is today maintained by Chet Ramey, a Senior Technology Architect at Case Western Reserve University. Ramey also maintains the Bash shell. Both projects were first authored by a Free Software Foundation employee named Brian Fox beginning in 1988. But Ramey has been the sole maintainer since around 1994.
|
||||
|
||||
Ramey told me via email that Readline, far from being an original idea, was created to implement functionality prescribed by the POSIX specification, which in the late 1980s had just been created. Many earlier shells, including the Korn shell and at least one version of the Unix System V shell, included line editing functionality. The 1988 version of the Korn shell (`ksh88`) provided both Emacs-style and Vi/Vim-style editing modes. As far as I can tell from [the manual page][2], the Korn shell would decide which mode you wanted to use by looking at the `VISUAL` and `EDITOR` environment variables, which is pretty neat. The parts of POSIX that specified shell functionality were closely modeled on `ksh88`, so GNU Bash was going to have to implement a similarly flexible line-editing system to stay compliant. Hence Readline.
|
||||
|
||||
When Ramey first got involved in Bash development, Readline was a single source file in the Bash project directory. It was really just a part of Bash. Over time, the Readline file slowly moved toward becoming an independent project, though it was not until 1994 (with the 2.0 release of Readline) that Readline became a separate library entirely.
|
||||
|
||||
Readline is closely associated with Bash, and Ramey usually pairs Readline releases with Bash releases. But as I mentioned above, Readline is a library that can be used by any software implementing a command-line interface. And it’s really easy to use. This is a simple example, but here’s how you would you use Readline in your own C program. The string argument to the `readline()` function is the prompt that you want Readline to display to the user:
|
||||
|
||||
```
|
||||
#include <stdio.h>
|
||||
#include <stdlib.h>
|
||||
#include "readline/readline.h"
|
||||
|
||||
int main(int argc, char** argv)
|
||||
{
|
||||
char* line = readline("my-rl-example> ");
|
||||
printf("You entered: \"%s\"\n", line);
|
||||
|
||||
free(line);
|
||||
|
||||
return 0;
|
||||
}
|
||||
```
|
||||
|
||||
Your program hands off control to Readline, which is responsible for getting a line of input from the user (in such a way that allows the user to do all the fancy line-editing things). Once the user has actually submitted the line, Readline returns it to you. I was able to compile the above by linking against the Readline library, which I apparently have somewhere in my library search path, by invoking the following:
|
||||
|
||||
```
|
||||
$ gcc main.c -lreadline
|
||||
```
|
||||
|
||||
The Readline API is much more extensive than that single function of course, and anyone using it can tweak all sorts of things about the library’s behavior. Library users can even add new functions that end users can configure via `~/.inputrc`, meaning that Readline is very easy to extend. But, as far as I can tell, even Bash ultimately calls the simple `readline()` function to get input just as in the example above, though there is a lot of configuration beforehand. (See [this line][3] in the source for GNU Bash, which seems to be where Bash hands off responsibility for getting input to Readline.)
|
||||
|
||||
Ramey has now worked on Bash and Readline for well over a decade. He has never once been compensated for his work—he is and has always been a volunteer. Bash and Readline continue to be actively developed, though Ramey said that Readline changes much more slowly than Bash does. I asked Ramey what it was like being the sole maintainer of software that so many people use. He said that millions of people probably use Bash without realizing it (because every Apple device runs Bash), which makes him worry about how much disruption a breaking change might cause. But he’s slowly gotten used to the idea of all those people out there. He said that he continues to work on Bash and Readline because at this point he is deeply invested and because he simply likes to make useful software available to the world.
|
||||
|
||||
_You can find more information about Chet Ramey at [his website][4]._
|
||||
|
||||
_If you enjoyed this post, more like it come out every four weeks! Follow [@TwoBitHistory][5] on Twitter or subscribe to the [RSS feed][6] to make sure you know when a new post is out._
|
||||
|
||||
_Previously on TwoBitHistory…_
|
||||
|
||||
> Please enjoy my long overdue new post, in which I use the story of the BBC Micro and the Computer Literacy Project as a springboard to complain about Codecademy.<https://t.co/PiWlKljDjK>
|
||||
>
|
||||
> — TwoBitHistory (@TwoBitHistory) [March 31, 2019][7]
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: https://twobithistory.org/2019/08/22/readline.html
|
||||
|
||||
作者：[Two-Bit History][a]
|
||||
选题：[lujun9972][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://twobithistory.org
|
||||
[b]: https://github.com/lujun9972
|
||||
[1]: https://tiswww.case.edu/php/chet/readline/readline.html
|
||||
[2]: https://web.archive.org/web/20151105130220/http://www2.research.att.com/sw/download/man/man1/ksh88.html
|
||||
[3]: https://github.com/bminor/bash/blob/9f597fd10993313262cab400bf3c46ffb3f6fd1e/parse.y#L1487
|
||||
[4]: https://tiswww.case.edu/php/chet/
|
||||
[5]: https://twitter.com/TwoBitHistory
|
||||
[6]: https://twobithistory.org/feed.xml
|
||||
[7]: https://twitter.com/TwoBitHistory/status/1112492084383092738?ref_src=twsrc%5Etfw
|
||||
@ -1,5 +1,5 @@
|
||||
[#]: collector: (lujun9972)
|
||||
[#]: translator: ( )
|
||||
[#]: translator: (gxlct008)
|
||||
[#]: reviewer: ( )
|
||||
[#]: publisher: ( )
|
||||
[#]: url: ( )
|
||||
|
||||
@ -1,5 +1,5 @@
|
||||
[#]: collector: (lujun9972)
|
||||
[#]: translator: ( )
|
||||
[#]: translator: (rakino)
|
||||
[#]: reviewer: ( )
|
||||
[#]: publisher: ( )
|
||||
[#]: url: ( )
|
||||
|
||||
@ -0,0 +1,136 @@
|
||||
[#]: collector: (lujun9972)
|
||||
[#]: translator: (rakino)
|
||||
[#]: reviewer: ( )
|
||||
[#]: publisher: ( )
|
||||
[#]: url: ( )
|
||||
[#]: subject: (Things You Didn't Know About GNU Readline)
|
||||
[#]: via: (https://twobithistory.org/2019/08/22/readline.html)
|
||||
[#]: author: (Two-Bit History https://twobithistory.org)
|
||||
|
||||
你所不知的 GNU Readline
|
||||
======
|
||||
|
||||
有时我会觉得自己的计算机是一栋非常大的房子，我每天都会访问这栋房子，也对一楼的大部分房间都了如指掌，但仍然还是有卧室我没有去过，有衣柜我没有打开过，有犄角旮旯我没有探索过。我感到有必要更多地了解我的计算机了，就像任何人都会觉得有必要看看自己家里从未去过的房间一样。
|
||||
|
||||
GNU Readline 是个不起眼的小软件库，我依赖了它多年却没有意识到它的存在，也许有成千上万的人每天都在不经意间使用它。如果你用 Bash shell 的话，每当你补全一个文件名，或者在一行文本输入中移动光标，以及搜索之前命令的历史记录时，你都在使用 GNU Readline；当你在 Postgres（`psql`）或是 Ruby REPL（`irb`）的命令行界面中进行同样的操作时，你依然在使用 GNU Readline。很多软件都依赖 GNU Readline 库来实现用户所期望的功能，不过这些功能是如此的辅助与不显眼，以至于在我看来很少有人会停下来去想它是从哪里来的。
|
||||
|
||||
GNU Readline 最初是自由软件基金会在 20 世纪 80 年代创建的，如今作为每个人的基础计算设施的重要组成部分的它，由一位志愿者维护。
|
||||
|
||||
### 充满特色
|
||||
|
||||
GNU Readline 库的存在，主要是为了用一组通用的按键来增强任何命令行界面，从而使你可以在一行输入中移动和编辑。例如，在 Bash 提示符中按下 `Ctrl-A`，你的光标会跳到行首，而按下 `Ctrl-E` 则会跳到行末；另一个有用的命令是 `Ctrl-U`，它会删除该行中光标之前的所有内容。
|
||||
|
||||
有很长一段时间，我通过反复敲击方向键来在命令行上移动，如今看来这十分尴尬，也不知道为什么，当时的我从来没有想过可以有一种更快的方法。当然了，没有一个熟悉 Vim 或 Emacs 这种文本编辑器的程序员愿意长时间地击打方向键，所以像 Readline 这样的东西必然会被创造出来；不过在 Readline 上可以做的绝非仅仅跳来跳去，你可以像使用文本编辑器那样编辑单行文本——这里有删除单词、换位、大写单词、复制和粘贴字符等命令。Readline 的大部分按键/快捷键都是基于 Emacs 的，它基本上就是一个单行文本版的 Emacs 了，甚至还有录制和重放宏的功能。
|
||||
|
||||
我从来没有用过 Emacs，所以很难记住所有不同的 Readline 命令。不过 Readline 有着很巧妙的一点，那就是能够切换到基于 Vim 的模式，在 Bash 中可以使用内置的 `set` 命令来这样做。下面会让 Readline 在当前的 shell 中使用 Vim 风格的命令：
|
||||
|
||||
```
|
||||
$ set -o vi
|
||||
```
|
||||
|
||||
该选项启用后，就可以使用 `dw` 等命令来删除单词了，此时相当于 Emacs 模式下的 `Ctrl-U` 的命令是 `d0`。
|
||||
|
||||
我第一次知道有这个功能的时候很兴奋地想尝试一下，但它对我来说并不是那么好用。我很高兴知道有这种对 Vim 用户的让步，在使用这个功能上你可能会比我更幸运，尤其是你还没有使用 Readline 的默认按键的话；我的问题在于，我听说有基于 Vim 的界面时已经学会了几种默认按键，因此即使启用了 Vim 的选项，也一直在错误地用着默认的按键；另外因为没有某种指示器，所以 Vim 的多模态设计在这里会很尴尬——你很容易就忘记了自己处于哪个模式，就因为这样，我卡在了一种虽然使用 Vim 作为文本编辑器，但却在 Readline 上用着 Emacs 风格的命令的情况里，我猜其他很多人也是这样的。
|
||||
|
||||
如果你觉得 Vim 和 Emacs 的键盘命令系统诡异而神秘，你可以按照喜欢的方式自定义 Readline 的键绑定，这并不难。Readline 在启动时会读取文件 `~/.inputrc`，它可以用来配置各种选项与键绑定，我做的一件事是重新配置了 `Ctrl-K`：通常情况下该命令会从光标处删除到行末，但我很少这样做，所以我在 `~/.inputrc` 中添加了以下内容，把它绑定为直接删除整行：
|
||||
|
||||
```
|
||||
Control-k: kill-whole-line
|
||||
```
|
||||
|
||||
每个 Readline 命令（文档中称它们为 _函数_ ）都有一个名称，你可以用这种方式将其与一个键序联系起来。如果你在 Vim 中编辑 `~/.inputrc`，就会发现 Vim 知道这种文件类型，还会帮你高亮显示有效的函数名，而不高亮无效的函数名。
|
||||
|
||||
`~/.inputrc` 可以做的另一件事是通过将键序映射到输入字符串上来创建预制宏。[Readline 手册][1]给出了一个我认为特别有用的例子：我经常想把一个程序的输出保存到文件中，这意味着我得经常在 Bash 命令中追加类似 `> output.txt` 这样的东西，为了节省时间，可以把它做成一个 Readline 宏。
|
||||
|
||||
```
|
||||
Control-o: "> output.txt"
|
||||
```
|
||||
|
||||
这样每当你按下 `Ctrl-O` 时，你都会看到 `> output.txt` 被添加到了命令行光标的后面，这样很不错！
|
||||
|
||||
不过你可以用宏做的可不仅仅是为文本串创建快捷方式；在 `~/.inputrc` 中使用以下条目意味着每次按下 `Ctrl-J` 时，行内已有的文本都会被 `$(` 和 `)` 包裹住。该宏先用 `Ctrl-A` 移动到行首，添加 `$(` ，然后再用 `Ctrl-E` 移动到行尾，添加 `)`。
|
||||
|
||||
```
|
||||
Control-j: "\C-a$(\C-e)"
|
||||
```
|
||||
|
||||
如果你经常需要像下面这样把一个命令的输出用于另一个命令的话，这个宏可能会对你有帮助。
|
||||
|
||||
```
|
||||
$ cd $(brew --prefix)
|
||||
```
|
||||
|
||||
`~/.inputrc` 文件也允许你为 Readline 手册中所谓的 _变量_ 设置不同的值，这些变量会启用或禁用某些 Readline 行为，你也可以使用这些变量来改变 Readline 中像是自动补全或者历史搜索这些行为的工作方式。我建议开启的一个变量是 `revert-all-at-newline`，它是默认关闭的，当这个变量关闭时，如果你使用反向搜索功能从命令历史记录中提取一行并编辑，但随后又决定搜索另一行，那么你所做的编辑会被保存在历史记录中。我觉得这样会很混乱，因为这会导致你的 Bash 命令历史中出现从未运行过的行。所以在你的 `~/.inputrc` 中加入这个：
|
||||
|
||||
```
|
||||
set revert-all-at-newline on
|
||||
```
|
||||
|
||||
在你用 `~/.inputrc` 设置了选项或键绑定以后，它们会适用于任何使用 Readline 库的地方，显然 Bash 包括在内，不过你也会在其它像是 `irb` 和 `psql` 这样的程序中受益。如果你经常使用关系型数据库的命令行界面，一个用于插入 `SELECT * FROM` 的 Readline 宏可能会很有用。
|
||||
|
||||
### Chet Ramey
|
||||
|
||||
GNU Readline 如今由凯斯西储大学的高级技术架构师 Chet Ramey 维护，Ramey 同时还负责维护 Bash shell；这两个项目都是由一位名叫 Brian Fox 的自由软件基金会员工在 1988 年开始编写的，但从 1994 年左右开始，Ramey 一直是它们唯一的维护者。
|
||||
|
||||
Ramey 通过电子邮件告诉我，Readline 远非一个原创的想法，它是为了实现 POSIX 规范所规定的功能而被创建的，而 POSIX 规范又是在 20 世纪 80 年代末被制定的。许多早期的 shell，包括 Korn shell 和至少一个版本的 Unix System V shell，都包含行编辑功能。1988 年版的 Korn shell（`ksh88`）提供了 Emacs 风格和 Vi/Vim 风格的编辑模式。据我从[手册页][2]中得知，Korn shell 会通过查看 `VISUAL` 和 `EDITOR` 环境变量来决定你使用的模式，这一点非常巧妙。POSIX 中指定 shell 功能的部分近似于 `ksh88` 的实现，所以 GNU Bash 也要实现一个类似的灵活的行编辑系统来保持兼容，因此就有了Readline。
|
||||
|
||||
Ramey 第一次参与 Bash 开发时，Readline 还是 Bash 项目目录下的一个源文件，它真的只是 Bash 的一部分；随着时间的推移，Readline 文件慢慢地成为了独立的项目，不过还要等到 1994 年（Readline 的 2.0 版本）Readline 才完全成为了一个独立的库。
|
||||
|
||||
Readline 与 Bash 密切相关，Ramey 也通常把 Readline 与 Bash 的发布配对，但正如我上面提到的，Readline 是一个可以被任何有命令行接口的软件使用的库，而且它真的很容易使用。下面是一个例子，虽然简单，但这就是在 C 程序中使用 Readline 的方法。向 `readline()` 函数传递的字符串参数就是你希望 Readline 向用户显示的提示符：
|
||||
|
||||
```
|
||||
#include <stdio.h>
|
||||
#include <stdlib.h>
|
||||
#include "readline/readline.h"
|
||||
|
||||
int main(int argc, char** argv)
|
||||
{
|
||||
char* line = readline("my-rl-example> ");
|
||||
printf("You entered: \"%s\"\n", line);
|
||||
|
||||
free(line);
|
||||
|
||||
return 0;
|
||||
}
|
||||
```
|
||||
|
||||
你的程序会把控制权交给 Readline，它会负责从用户那里获得一行输入（以这样的方式让用户可以做所有花哨的行编辑工作），一旦用户真正提交了这一行，Readline 就会把它返回给你。在我的库搜索路径中有 Readline 库，所以我可以通过调用以下内容来链接 Readline 库，从而编译上面的内容：
|
||||
|
||||
```
|
||||
$ gcc main.c -lreadline
|
||||
```
|
||||
|
||||
当然，Readline 的 API 比起那个单一的函数要丰富得多，任何使用它的人都可以对库的行为进行各种调整，库的用户（开发者）甚至可以添加新的函数，来让最终用户可以通过 `~/.inputrc` 来配置它们，这意味着 Readline 非常容易扩展。但是据我所知，即使是 Bash ，虽然事先有很多配置，最终也会像上面的例子一样调用简单的 `readline()` 函数来获取输入。（参见 GNU Bash 源代码中的[这一行][3]，Bash 似乎在这里将获取输入的责任交给了 Readline）。
|
||||
|
||||
Ramey 现在已经在 Bash 和 Readline 上工作了十多年，但他的工作却从来没有得到过报酬——他一直都是一名志愿者。尽管 Ramey 说 Readline 的变化比 Bash 慢得多，但 Bash 和 Readline 仍然在积极开发中。我问 Ramey 作为这么多人使用的软件唯一的维护者是什么感觉，他说可能有几百万人在不知不觉中使用 Bash（因为每个苹果设备都运行 Bash），这让他担心一个突破性的变化会造成多大的破坏，不过他已经慢慢习惯了所有这些人的想法。他还说他会继续在 Bash 和 Readline 上工作，因为在这一点上他已经深深地投入了，而且他也只是单纯地喜欢把有用的软件提供给世界。
|
||||
|
||||
_你可以在 [Chet Ramey 的网站][4]上找到更多关于他的信息。_
|
||||
|
||||
_喜欢这篇文章吗？我会每四周写出一篇像这样的文章。关注推特帐号 [@TwoBitHistory][5] 或者[订阅 RSS][6] 来获取更新吧！_
|
||||
|
||||
_TwoBitHistory 的上一条消息：_
|
||||
|
||||
> 请欣赏我拖欠已久的新文章，我在里面以 BBC Micro 和计算机认知计划的故事作为出发点抱怨了一下 Codecademy。<https://t.co/PiWlKljDjK>
|
||||
>
|
||||
> — TwoBitHistory (@TwoBitHistory) [三月 31，2019][7]
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: https://twobithistory.org/2019/08/22/readline.html
|
||||
|
||||
作者：[Two-Bit History][a]
|
||||
选题：[lujun9972][b]
|
||||
译者：[rakino](https://github.com/rakino)
|
||||
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://twobithistory.org
|
||||
[b]: https://github.com/lujun9972
|
||||
[1]: https://tiswww.case.edu/php/chet/readline/readline.html
|
||||
[2]: https://web.archive.org/web/20151105130220/http://www2.research.att.com/sw/download/man/man1/ksh88.html
|
||||
[3]: https://github.com/bminor/bash/blob/9f597fd10993313262cab400bf3c46ffb3f6fd1e/parse.y#L1487
|
||||
[4]: https://tiswww.case.edu/php/chet/
|
||||
[5]: https://twitter.com/TwoBitHistory
|
||||
[6]: https://twobithistory.org/feed.xml
|
||||
[7]: https://twitter.com/TwoBitHistory/status/1112492084383092738?ref_src=twsrc%5Etfw
|
||||
Loading…
Reference in New Issue
Block a user