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@ -1,8 +1,8 @@
|
||||
[#]: collector: (lujun9972)
|
||||
[#]: translator: (wxy)
|
||||
[#]: reviewer: (wxy)
|
||||
[#]: publisher: ( )
|
||||
[#]: url: ( )
|
||||
[#]: publisher: (wxy)
|
||||
[#]: url: (https://linux.cn/article-12979-1.html)
|
||||
[#]: subject: (Learn Rust by writing a simple game)
|
||||
[#]: via: (https://opensource.com/article/20/12/learn-rust)
|
||||
[#]: author: (Moshe Zadka https://opensource.com/users/moshez)
|
||||
128
published/20201225 How to use heredoc as a text editor.md
Normal file
128
published/20201225 How to use heredoc as a text editor.md
Normal file
@ -0,0 +1,128 @@
|
||||
[#]: collector: (lujun9972)
|
||||
[#]: translator: (geekpi)
|
||||
[#]: reviewer: (wxy)
|
||||
[#]: publisher: (wxy)
|
||||
[#]: url: (https://linux.cn/article-12978-1.html)
|
||||
[#]: subject: (How to use heredoc as a text editor)
|
||||
[#]: via: (https://opensource.com/article/20/12/heredoc)
|
||||
[#]: author: (Seth Kenlon https://opensource.com/users/seth)
|
||||
|
||||
如何使用 heredoc 作为一个文本编辑器
|
||||
======
|
||||
|
||||
> 这个不起眼的终端功能在紧要关头提供一个文本编辑器。
|
||||
|
||||
|
||||
|
||||
在 Linux 和 Unix 的 shell 中有一个不为人知的功能，它能让你用 [cat][2] 命令打开一个 do-while 循环。它被称为 heredoc，无论你使用什么 shell，它都能让你或多或少地拥有一个文本编辑器。它的语法是：
|
||||
|
||||
```
|
||||
$ cat << EOF >> example.txt
|
||||
```
|
||||
|
||||
中间的字符串（`EOF`），本质上是一个停止循环的条件。也就是说，如果你在一行中单独输入它，循环就会结束。在循环过程中，无论你在终端中输入什么，都会被管道传送到目标文件中（在本例中）。
|
||||
|
||||
### 安装
|
||||
|
||||
只要你有一个终端，你就能够启动 heredoc。我在 [Bash][3]、[tsh][4] 和 Korn shell 中使用过这个语法技巧。
|
||||
|
||||
### 使用 heredoc
|
||||
|
||||
要打开一个 heredoc “会话”，你可以使用带重定向的 `cat` 命令。首先用终止字符串（常见约定是 `EOF`，代表 “End Of File”，但它实际上可以是任何字符串）指向 `cat` 命令。在终止字符串之后，将输出重定向到一个目标文件。然后，你就可以直接在终端中输入了，可以使用最常见的 shell 键盘快捷键来处理你的工作。当你在一行上输入你指定的终止字符串时，你的会话就结束了。你可以通过唯一的提示符（通常是 `>`）知道你是在一个 heredoc 循环中。
|
||||
|
||||
```
|
||||
$ cat << EOF >> example.txt
|
||||
> Everything you type here will be placed into example.txt when I type EOF on a line by itself. Until then, you can type...
|
||||
>
|
||||
> whatever...
|
||||
>
|
||||
> you want to type.
|
||||
>
|
||||
> EOF
|
||||
$
|
||||
```
|
||||
|
||||
在终端等待 `EOF` 时，你输入的所有内容都会被放入目标文件中，提示符被忽略，`EOF` 本身也不是文件的一部分。
|
||||
|
||||
```
|
||||
Everything you type here will be placed into example.txt when I type EOF on a line by itself. Until then, you can type...
|
||||
|
||||
whatever...
|
||||
|
||||
you want to type.
|
||||
```
|
||||
|
||||
在现实中，你可能不会用 heredoc 语法来代替一个正常的文本编辑器。它是一个很好的快速处理方式，可以输入多行，但超过 10 行左右就开始限制它的作用了。例如，如果不触发你 shell 的 [history][5] 功能，你就不能编辑以前的行。根据你的 shell 和配置，你可能需要先按向上键，然后按向下键来找回你的文本，然后用 `Ctrl+B` 来后退。
|
||||
|
||||
你的 shell 的大部分功能都能正常工作，但可能没有撤销功能，也没有什么错误恢复功能。
|
||||
|
||||
此外，即使是最简安装的系统，可能也至少安装了 [Vi][6] 或 [ed][7]。
|
||||
|
||||
然而 heredoc 还是很有用的！它比 `echo` 更灵活，当你在编写 shell 脚本时，它是不可缺少的。例如，想象一下你正在编写一个安装脚本，以便你可以自动安装一组自定义应用。其中一个应用没有生成 `.dekstop` 文件，所以它不会出现在你的应用菜单中。为了解决这个问题，你决定在安装时生成一个 `.desktop` 文件。
|
||||
|
||||
与其编写一个 `.desktop` 文件，然后作为安装脚本的外部依赖，不如在安装脚本中使用 heredoc：
|
||||
|
||||
```
|
||||
#!/bin/sh
|
||||
|
||||
VERSION=${VERSION:-x.y.z}
|
||||
PKGNAM=${VERSION:-example}
|
||||
PKG="${PKGNAM}"-"${VERSION}"-`arch`.tgz
|
||||
|
||||
# download package
|
||||
wget "${PKG}"
|
||||
tar txvf "${PKG}"
|
||||
|
||||
# use here doc to create missing .desktop file
|
||||
cat << EOF >> $HOME/.local/share/applications/example.desktop
|
||||
[Desktop Entry]
|
||||
Version=1.0
|
||||
Type=Application
|
||||
Name="${PKGNAM}"
|
||||
Comment="${PKGNAM}"
|
||||
Exec="${PKGNAM}" %F
|
||||
EOF
|
||||
|
||||
# insert the rest of an install script...
|
||||
```
|
||||
|
||||
你自动地将文本输入到了一个文件中，而不需要文本编辑器（当然，除了你用来写脚本的那个）。下面是生成的 `.desktop` 文件的样子：
|
||||
|
||||
```
|
||||
[Desktop Entry]
|
||||
Version=1.0
|
||||
Type=Application
|
||||
Name=example
|
||||
Comment=example
|
||||
Exec=example %F
|
||||
```
|
||||
|
||||
正如你所看到的，你可以在 heredoc 中使用变量，而且它们得到了正确的解析。`EOF` 字符串并没有出现在文件中，它只是标志着 heredoc 的结束。
|
||||
|
||||
### 比 echo 更好
|
||||
|
||||
heredoc 技术通常被认为比 `echo` 或 [printf][8] 更容易，因为一旦你“进入”了文档，你就可以自由地做任何你想做的事情。从这个意义上说，它是自由的，但与合适的文本编辑器相比，它是有限的。
|
||||
|
||||
使用 heredoc 来做快速笔记和 shell 脚本，再也不用为如何动态生成配置文件而烦恼了。
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: https://opensource.com/article/20/12/heredoc
|
||||
|
||||
作者：[Seth Kenlon][a]
|
||||
选题：[lujun9972][b]
|
||||
译者：[geekpi](https://github.com/geekpi)
|
||||
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
|
||||
|
||||
[a]: https://opensource.com/users/seth
|
||||
[b]: https://github.com/lujun9972
|
||||
[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/lenovo-thinkpad-laptop-window-focus.png?itok=g0xPm2kD (young woman working on a laptop)
|
||||
[2]: https://opensource.com/article/19/2/getting-started-cat-command
|
||||
[3]: https://opensource.com/article/20/4/bash-sysadmins-ebook
|
||||
[4]: https://opensource.com/article/20/8/tcsh
|
||||
[5]: https://opensource.com/article/20/6/bash-history-commands
|
||||
[6]: https://opensource.com/article/19/3/getting-started-vim
|
||||
[7]: https://opensource.com/article/20/12/gnu-ed
|
||||
[8]: https://opensource.com/article/20/8/printf
|
||||
@ -1,5 +1,5 @@
|
||||
[#]: collector: (lujun9972)
|
||||
[#]: translator: ( )
|
||||
[#]: translator: (FSSlc)
|
||||
[#]: reviewer: ( )
|
||||
[#]: publisher: ( )
|
||||
[#]: url: ( )
|
||||
|
||||
@ -1,5 +1,5 @@
|
||||
[#]: collector: (lujun9972)
|
||||
[#]: translator: ( )
|
||||
[#]: translator: (lxbwolf)
|
||||
[#]: reviewer: ( )
|
||||
[#]: publisher: ( )
|
||||
[#]: url: ( )
|
||||
|
||||
@ -0,0 +1,101 @@
|
||||
[#]: collector: (lujun9972)
|
||||
[#]: translator: ( )
|
||||
[#]: reviewer: ( )
|
||||
[#]: publisher: ( )
|
||||
[#]: url: ( )
|
||||
[#]: subject: (Explore the night sky with this open source astronomy app)
|
||||
[#]: via: (https://opensource.com/article/21/1/kstars)
|
||||
[#]: author: (Don Watkins https://opensource.com/users/don-watkins)
|
||||
|
||||
Explore the night sky with this open source astronomy app
|
||||
======
|
||||
Stargaze from your Linux desktop or Android device with KStars.
|
||||
![Open source stars.][1]
|
||||
|
||||
I have always been fascinated with the night sky. When I was younger, the only reference materials available were books, and they seemed to depict a sky that looked different from the one I saw from my home.
|
||||
|
||||
More than five years ago, I wrote about my experiences with two open source planetarium apps, [Celestia and Stellarium][2]. Recently, I read about another: [KStars][3]. It's an amazing open source application that helps engage children (and adults) in science and astronomy. Its website says:
|
||||
|
||||
> "KStars is free, open source, cross-platform astronomy software. It provides an accurate graphical simulation of the night sky, from any location on Earth, at any date and time. The display includes up to 100 million stars, 13,000 deep-sky objects, all 8 planets, the Sun and Moon, and thousands of comets, asteroids, supernovae, and satellites."
|
||||
|
||||
KStars is part of the [KDE Education Project][4]. The latest version, available for Linux, Windows, and macOS, integrates [StellarSolver][5], a cross-platform SExtractor, a program that builds a catalog of objects from an astronomical image.
|
||||
|
||||
### Installing KStars
|
||||
|
||||
KStars is freely licensed under the GPLv2.0. The source code is available on the official [KDE GitLab instance][6] and as a read-only mirror on GitHub. The KDE Education Project has excellent [installation documentation][7].
|
||||
|
||||
I'm using [Pop!_OS][8] and found KStars in the Pop!_Shop.
|
||||
|
||||
You can install KStars on Linux from your distribution's software repository. KStars Lite is available for Android from the [Google Play store][9]. The KDE Project maintains an excellent [KStars Handbook][10] to assist users.
|
||||
|
||||
### Using KStars
|
||||
|
||||
After installation, launch the program from your Applications menu. A startup wizard guides you through the initial setup.
|
||||
|
||||
![KStars Startup Wizard][11]
|
||||
|
||||
(Don Watkins, [CC BY-SA 4.0][12])
|
||||
|
||||
The directions are easy to follow. The wizard prompts you to set your home location; unfortunately, my small village was not listed, but a larger nearby community was.
|
||||
|
||||
![KStars location setup][13]
|
||||
|
||||
(Don Watkins, [CC BY-SA 4.0][12])
|
||||
|
||||
You also have the opportunity to download additional data and extra features for the program.
|
||||
|
||||
![KStars add-ons][14]
|
||||
|
||||
(Don Watkins, [CC BY-SA 4.0][12])
|
||||
|
||||
There are many options available. I chose "Common images displayed in the detail window."
|
||||
|
||||
Once you're finished with the setup, KStars presents a map of the night sky as it appears from your location.
|
||||
|
||||
![KStars night sky display][15]
|
||||
|
||||
(Don Watkins, [CC BY-SA 4.0][12])
|
||||
|
||||
It displays the current local time in the upper-left corner (5:58pm on November 30, 2020, in this image).
|
||||
|
||||
Using the left mouse button, you can move the display left, right, up, and down. You can zoom in and out using the mouse's scroll wheel. Placing the mouse cursor over an object and right-clicking describes the object you're looking at.
|
||||
|
||||
![KStars describes objects][16]
|
||||
|
||||
(Don Watkins, [CC BY-SA 4.0][12])
|
||||
|
||||
### Get involved
|
||||
|
||||
KStars is actively soliciting help with bug reports, astronomy knowledge, code, translations, and more. The lead developer and maintainer is [Jasem Mutlaq][17]. If you'd like to contribute, please visit the [project's website][18] or join the mailing list to learn more.
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: https://opensource.com/article/21/1/kstars
|
||||
|
||||
作者：[Don Watkins][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://opensource.com/users/don-watkins
|
||||
[b]: https://github.com/lujun9972
|
||||
[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/osdc_520x292_opensourcestars.png?itok=hnrMETFh (Open source stars.)
|
||||
[2]: https://opensource.com/education/15/7/open-source-apps-explore-night-sky
|
||||
[3]: https://edu.kde.org/kstars/
|
||||
[4]: https://edu.kde.org/
|
||||
[5]: https://github.com/rlancaste/stellarsolver
|
||||
[6]: https://invent.kde.org/education/kstars
|
||||
[7]: https://edu.kde.org/kstars/install.php
|
||||
[8]: https://pop.system76.com/
|
||||
[9]: https://play.google.com/store/apps/details?id=org.kde.kstars.lite&hl=en
|
||||
[10]: https://docs.kde.org/trunk5/en/extragear-edu/kstars/index.html
|
||||
[11]: https://opensource.com/sites/default/files/uploads/kstars_startupwizard.png (KStars Startup Wizard)
|
||||
[12]: https://creativecommons.org/licenses/by-sa/4.0/
|
||||
[13]: https://opensource.com/sites/default/files/uploads/kstars_setlocation.png (KStars location setup)
|
||||
[14]: https://opensource.com/sites/default/files/uploads/kstars_addons.png (KStars add-ons)
|
||||
[15]: https://opensource.com/sites/default/files/uploads/kstars_sky.png (KStars night sky display)
|
||||
[16]: https://opensource.com/sites/default/files/uploads/kstars_objectdescription.png (KStars describes objects)
|
||||
[17]: https://github.com/knro
|
||||
[18]: https://edu.kde.org/kstars
|
||||
@ -1,131 +0,0 @@
|
||||
[#]: collector: (lujun9972)
|
||||
[#]: translator: (geekpi)
|
||||
[#]: reviewer: ( )
|
||||
[#]: publisher: ( )
|
||||
[#]: url: ( )
|
||||
[#]: subject: (How to use heredoc as a text editor)
|
||||
[#]: via: (https://opensource.com/article/20/12/heredoc)
|
||||
[#]: author: (Seth Kenlon https://opensource.com/users/seth)
|
||||
|
||||
如何使用 heredoc 作为一个文本编辑器
|
||||
======
|
||||
这个不起眼的终端功能在紧要关头提供了一个文本编辑器。
|
||||
![woman on laptop sitting at the window][1]
|
||||
|
||||
在 Linux 和 Unix shells 中有一个不为人知的功能，它能让你为 [cat][2] 命令打开一个 do-while 循环。它被称为 _heredoc_，无论你使用什么 shell，它都能让你或多或少地拥有一个文本编辑器。它的语法是：
|
||||
|
||||
|
||||
```
|
||||
`$ cat << EOF >> example.txt`
|
||||
```
|
||||
|
||||
中间的字符串，本质上是一个停止循环的条件。也就是说，如果你在一行中单独输入它，循环就会结束。在循环过程中，无论你在终端中输入什么，都会被管道传送到目标文件中（在本例中）。
|
||||
|
||||
### 安装
|
||||
|
||||
只要你有一个终端，你就能够启动 heredoc。我在 [Bash][3]、[tsh][4] 和 Korn shell 中使用过这个语法技巧。
|
||||
|
||||
### 使用 heredoc
|
||||
|
||||
要打开一个 heredoc “会话”，你可以使用 cat 命令重定向，它首先指向具有终止字符串的 cat（常见约定是 **EOF**，代表 “End Of File”，但它实际上可以是任何东西））。在终止关键字之后，你将输出重定向到一个目标文件。然后，你就可以直接在终端中输入，使用最常见的 shell 键盘快捷键来处理你的工作。当你在一行上输入你指定的终止字符串时，你的会话就结束了。你可以通过唯一的提示符（通常是 **>**）知道你是在一个 heredoc 循环中。
|
||||
|
||||
|
||||
```
|
||||
$ cat << EOF >> example.txt
|
||||
> Everything you type here will be placed into example.txt when I type EOF on a line by itself. Until then, you can type...
|
||||
>
|
||||
> whatever...
|
||||
>
|
||||
> you want to type.
|
||||
>
|
||||
> EOF
|
||||
$
|
||||
```
|
||||
|
||||
在终端等待 **EOF** 时，你输入的所有内容都会被放入目标文件中，提示符被省略，EOF 本身也不是文件的一部分。
|
||||
|
||||
|
||||
```
|
||||
Everything you type here will be placed into example.txt when I type EOF on a line by itself. Until then, you can type...
|
||||
|
||||
whatever...
|
||||
|
||||
you want to type.
|
||||
```
|
||||
|
||||
现实中，你可能不会用 heredoc 语法来代替一个好的文本编辑器。它是一个很好的快速处理，可以输入多行，但超过 10 行左右就开始限制它的作用了。例如，如果不触发你 shell 的 [history][5] 功能，你就不能编辑以前的行。根据你的 shell 和配置，你可能可以先向上，然后向下来调用你的文本，然后用 **Ctrl+B** 来后退。
|
||||
|
||||
你的 shell 的大部分功能都能正常工作，但可能没有撤销功能，也没有什么错误恢复功能。
|
||||
|
||||
此外，即使是最简安装，也可能至少安装了 [Vi][6] 或 [ed][7]。
|
||||
|
||||
然而 heredoc 还是很有用的！它比 **echo** 更灵活，当你在使用 shell 脚本时，它是不可缺少的。例如，想象一下你正在编写一个安装脚本，这样你就可以自动安装一组自定义应用。其中一个应用没有生成 `.dekstop`文件，所以它不会出现在你的应用菜单中。为了解决这个问题，你决定在安装时生成一个 `.desktop` 文件。
|
||||
|
||||
与其编写一个 `.desktop` 文件，然后作为安装脚本的外部依赖，不如在安装脚本中使用 heredoc：
|
||||
|
||||
|
||||
```
|
||||
#!/bin/sh
|
||||
|
||||
VERSION=${VERSION:-x.y.z}
|
||||
PKGNAM=${VERSION:-example}
|
||||
PKG="${PKGNAM}"-"${VERSION}"-`arch`.tgz
|
||||
|
||||
# download package
|
||||
wget "${PKG}"
|
||||
tar txvf "${PKG}"
|
||||
|
||||
# use here doc to create missing .desktop file
|
||||
cat << EOF >> $HOME/.local/share/applications/example.desktop
|
||||
[Desktop Entry]
|
||||
Version=1.0
|
||||
Type=Application
|
||||
Name="${PKGNAM}"
|
||||
Comment="${PKGNAM}"
|
||||
Exec="${PKGNAM}" %F
|
||||
EOF
|
||||
|
||||
# insert the rest of an install script...
|
||||
```
|
||||
|
||||
你可以自动将文本输入到一个文件中，不需要文本编辑器（当然，除了你用来写脚本的那个）。下面是生成的 `.desktop` 文件的样子：
|
||||
|
||||
|
||||
```
|
||||
[Desktop Entry]
|
||||
Version=1.0
|
||||
Type=Application
|
||||
Name=example
|
||||
Comment=example
|
||||
Exec=example %F
|
||||
```
|
||||
|
||||
正如你所看到的，你可以在 heredoc 中使用变量，而且它们得到了正确的解析。`EOF` 字符串并没有出现在文件中，它只是标志着 heredoc 的结束。
|
||||
|
||||
### 比 echo 更好
|
||||
|
||||
heredoc 技术通常被认为比 `echo` 或 [printf][8] 更容易，因为一旦你“进入”了文档，你就可以自由地做任何你想做的事情。从这个意义上说，它是自由的，但与合适的文本编辑器相比，它是有限的。
|
||||
|
||||
使用 heredoc 来做快速笔记和 shell 脚本，再也不用为如何动态生成配置文件而烦恼了。
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: https://opensource.com/article/20/12/heredoc
|
||||
|
||||
作者：[Seth Kenlon][a]
|
||||
选题：[lujun9972][b]
|
||||
译者：[geekpi](https://github.com/geekpi)
|
||||
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://opensource.com/users/seth
|
||||
[b]: https://github.com/lujun9972
|
||||
[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/lenovo-thinkpad-laptop-window-focus.png?itok=g0xPm2kD (young woman working on a laptop)
|
||||
[2]: https://opensource.com/article/19/2/getting-started-cat-command
|
||||
[3]: https://opensource.com/article/20/4/bash-sysadmins-ebook
|
||||
[4]: https://opensource.com/article/20/8/tcsh
|
||||
[5]: https://opensource.com/article/20/6/bash-history-commands
|
||||
[6]: https://opensource.com/article/19/3/getting-started-vim
|
||||
[7]: https://opensource.com/article/20/12/gnu-ed
|
||||
[8]: https://opensource.com/article/20/8/printf
|
||||
Loading…
Reference in New Issue
Block a user