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published/20191023 How to program with Bash- Loops.md
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published/20191023 How to program with Bash- Loops.md
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[#]: collector: (lujun9972)
|
||||
[#]: translator: (lxbwolf)
|
||||
[#]: reviewer: (wxy)
|
||||
[#]: publisher: (wxy)
|
||||
[#]: url: (https://linux.cn/article-11714-1.html)
|
||||
[#]: subject: (How to program with Bash: Loops)
|
||||
[#]: via: (https://opensource.com/article/19/10/programming-bash-loops)
|
||||
[#]: author: (David Both https://opensource.com/users/dboth)
|
||||
|
||||
怎样用 Bash 编程：循环
|
||||
======
|
||||
|
||||
> 本文是 Bash 编程系列三篇中的最后一篇，来学习使用循环执行迭代的操作。
|
||||
|
||||
|
||||
|
||||
Bash 是一种强大的用于命令行和 shell 脚本的编程语言。本系列的三部分都是基于我的三集 [Linux 自学课程][2] 写的，探索怎么用 CLI 进行 bash 编程。
|
||||
|
||||
本系列的 [第一篇文章][3] 讨论了 bash 编程的一些简单命令行操作，如使用变量和控制操作符。[第二篇文章][4] 探讨了文件、字符串、数字等类型和各种各样在执行流中提供控制逻辑的的逻辑运算符，还有 bash 中不同种类的扩展。本文是第三篇（也是最后一篇），意在考察在各种迭代的操作中使用循环以及怎么合理控制循环。
|
||||
|
||||
### 循环
|
||||
|
||||
我使用过的所有编程语言都至少有两种循环结构来用来执行重复的操作。我经常使用 `for` 循环，然而我发现 `while` 和 `until` 循环也很有用处。
|
||||
|
||||
#### for 循环
|
||||
|
||||
我的理解是，在 bash 中实现的 `for` 命令比大部分语言灵活，因为它可以处理非数字的值；与之形成对比的是，诸如标准 C 语言的 `for` 循环只能处理数字类型的值。
|
||||
|
||||
Bash 版的 `for` 命令基本的结构很简单：
|
||||
|
||||
```
|
||||
for Var in list1 ; do list2 ; done
|
||||
```
|
||||
|
||||
解释一下：“对于 `list1` 中的每一个值，把 `$Var` 设置为那个值，使用该值执行 `list2` 中的程序语句；`list1` 中的值都执行完后，整个循环结束，退出循环。” `list1` 中的值可以是一个简单的显式字符串值，也可以是一个命令执行后的结果（`` 包含其内的命令执行的结果，本系列第二篇文章中有描述）。我经常使用这种结构。
|
||||
|
||||
要测试它，确认 `~/testdir` 仍然是当前的工作目录（PWD）。删除目录下所有东西，来看下这个显式写出值列表的 `for` 循环的简单的示例。这个列表混合了字母和数字 — 但是不要忘了，在 bash 中所有的变量都是字符串或者可以被当成字符串来处理。
|
||||
|
||||
```
|
||||
[student@studentvm1 testdir]$ rm *
|
||||
[student@studentvm1 testdir]$ for I in a b c d 1 2 3 4 ; do echo $I ; done
|
||||
a
|
||||
b
|
||||
c
|
||||
d
|
||||
1
|
||||
2
|
||||
3
|
||||
4
|
||||
```
|
||||
|
||||
给变量赋予更有意义的名字，变成前面版本的进阶版：
|
||||
|
||||
```
|
||||
[student@studentvm1 testdir]$ for Dept in "Human Resources" Sales Finance "Information Technology" Engineering Administration Research ; do echo "Department $Dept" ; done
|
||||
Department Human Resources
|
||||
Department Sales
|
||||
Department Finance
|
||||
Department Information Technology
|
||||
Department Engineering
|
||||
Department Administration
|
||||
Department Research
|
||||
```
|
||||
|
||||
创建几个目录（创建时显示一些处理信息）：
|
||||
|
||||
```
|
||||
[student@studentvm1 testdir]$ for Dept in "Human Resources" Sales Finance "Information Technology" Engineering Administration Research ; do echo "Working on Department $Dept" ; mkdir "$Dept" ; done
|
||||
Working on Department Human Resources
|
||||
Working on Department Sales
|
||||
Working on Department Finance
|
||||
Working on Department Information Technology
|
||||
Working on Department Engineering
|
||||
Working on Department Administration
|
||||
Working on Department Research
|
||||
[student@studentvm1 testdir]$ ll
|
||||
total 28
|
||||
drwxrwxr-x 2 student student 4096 Apr 8 15:45 Administration
|
||||
drwxrwxr-x 2 student student 4096 Apr 8 15:45 Engineering
|
||||
drwxrwxr-x 2 student student 4096 Apr 8 15:45 Finance
|
||||
drwxrwxr-x 2 student student 4096 Apr 8 15:45 'Human Resources'
|
||||
drwxrwxr-x 2 student student 4096 Apr 8 15:45 'Information Technology'
|
||||
drwxrwxr-x 2 student student 4096 Apr 8 15:45 Research
|
||||
drwxrwxr-x 2 student student 4096 Apr 8 15:45 Sales
|
||||
```
|
||||
|
||||
在 `mkdir` 语句中 `$Dept` 变量必须用引号包裹起来；否则名字中间有空格（如 `Information Technology`）会被当做两个独立的目录处理。我一直信奉的一条实践规则：所有的文件和目录都应该为一个单词（中间没有空格）。虽然大部分现代的操作系统可以处理名字中间有空格的情况，但是系统管理员需要花费额外的精力去确保脚本和 CLI 程序能正确处理这些特例。（即使它们很烦人，也务必考虑它们，因为你永远不知道将拥有哪些文件。）
|
||||
|
||||
再次删除 `~/testdir` 下的所有东西 — 再运行一次下面的命令：
|
||||
|
||||
```
|
||||
[student@studentvm1 testdir]$ rm -rf * ; ll
|
||||
total 0
|
||||
[student@studentvm1 testdir]$ for Dept in Human-Resources Sales Finance Information-Technology Engineering Administration Research ; do echo "Working on Department $Dept" ; mkdir "$Dept" ; done
|
||||
Working on Department Human-Resources
|
||||
Working on Department Sales
|
||||
Working on Department Finance
|
||||
Working on Department Information-Technology
|
||||
Working on Department Engineering
|
||||
Working on Department Administration
|
||||
Working on Department Research
|
||||
[student@studentvm1 testdir]$ ll
|
||||
total 28
|
||||
drwxrwxr-x 2 student student 4096 Apr 8 15:52 Administration
|
||||
drwxrwxr-x 2 student student 4096 Apr 8 15:52 Engineering
|
||||
drwxrwxr-x 2 student student 4096 Apr 8 15:52 Finance
|
||||
drwxrwxr-x 2 student student 4096 Apr 8 15:52 Human-Resources
|
||||
drwxrwxr-x 2 student student 4096 Apr 8 15:52 Information-Technology
|
||||
drwxrwxr-x 2 student student 4096 Apr 8 15:52 Research
|
||||
drwxrwxr-x 2 student student 4096 Apr 8 15:52 Sales
|
||||
```
|
||||
|
||||
假设现在有个需求，需要列出一台 Linux 机器上所有的 RPM 包并对每个包附上简短的描述。我为北卡罗来纳州工作的时候，曾经遇到过这种需求。由于当时开源尚未得到州政府的“批准”，而且我只在台式机上使用 Linux，对技术一窍不通的老板（PHB）需要我列出我计算机上安装的所有软件，以便他们可以“批准”一个特例。
|
||||
|
||||
你怎么实现它？有一种方法是，已知 `rpm –qa` 命令提供了 RPM 包的完整描述，包括了白痴老板想要的东西：软件名称和概要描述。
|
||||
|
||||
让我们一步步执行出最后的结果。首先，列出所有的 RPM 包：
|
||||
|
||||
```
|
||||
[student@studentvm1 testdir]$ rpm -qa
|
||||
perl-HTTP-Message-6.18-3.fc29.noarch
|
||||
perl-IO-1.39-427.fc29.x86_64
|
||||
perl-Math-Complex-1.59-429.fc29.noarch
|
||||
lua-5.3.5-2.fc29.x86_64
|
||||
java-11-openjdk-headless-11.0.ea.28-2.fc29.x86_64
|
||||
util-linux-2.32.1-1.fc29.x86_64
|
||||
libreport-fedora-2.9.7-1.fc29.x86_64
|
||||
rpcbind-1.2.5-0.fc29.x86_64
|
||||
libsss_sudo-2.0.0-5.fc29.x86_64
|
||||
libfontenc-1.1.3-9.fc29.x86_64
|
||||
<snip>
|
||||
```
|
||||
|
||||
用 `sort` 和 `uniq` 命令对列表进行排序和打印去重后的结果（有些已安装的 RPM 包具有相同的名字）：
|
||||
|
||||
|
||||
```
|
||||
[student@studentvm1 testdir]$ rpm -qa | sort | uniq
|
||||
a2ps-4.14-39.fc29.x86_64
|
||||
aajohan-comfortaa-fonts-3.001-3.fc29.noarch
|
||||
abattis-cantarell-fonts-0.111-1.fc29.noarch
|
||||
abiword-3.0.2-13.fc29.x86_64
|
||||
abrt-2.11.0-1.fc29.x86_64
|
||||
abrt-addon-ccpp-2.11.0-1.fc29.x86_64
|
||||
abrt-addon-coredump-helper-2.11.0-1.fc29.x86_64
|
||||
abrt-addon-kerneloops-2.11.0-1.fc29.x86_64
|
||||
abrt-addon-pstoreoops-2.11.0-1.fc29.x86_64
|
||||
abrt-addon-vmcore-2.11.0-1.fc29.x86_64
|
||||
<snip>
|
||||
```
|
||||
|
||||
以上命令得到了想要的 RPM 列表，因此你可以把这个列表作为一个循环的输入信息，循环最终会打印每个 RPM 包的详细信息：
|
||||
|
||||
```
|
||||
[student@studentvm1 testdir]$ for RPM in `rpm -qa | sort | uniq` ; do rpm -qi $RPM ; done
|
||||
```
|
||||
|
||||
这段代码产出了多余的信息。当循环结束后，下一步就是提取出白痴老板需要的信息。因此，添加一个 `egrep` 命令用来搜索匹配 `^Name` 或 `^Summary` 的行。脱字符（`^`）表示行首，整个命令表示显示所有以 Name 或 Summary 开头的行。
|
||||
|
||||
```
|
||||
[student@studentvm1 testdir]$ for RPM in `rpm -qa | sort | uniq` ; do rpm -qi $RPM ; done | egrep -i "^Name|^Summary"
|
||||
Name : a2ps
|
||||
Summary : Converts text and other types of files to PostScript
|
||||
Name : aajohan-comfortaa-fonts
|
||||
Summary : Modern style true type font
|
||||
Name : abattis-cantarell-fonts
|
||||
Summary : Humanist sans serif font
|
||||
Name : abiword
|
||||
Summary : Word processing program
|
||||
Name : abrt
|
||||
Summary : Automatic bug detection and reporting tool
|
||||
<snip>
|
||||
```
|
||||
|
||||
在上面的命令中你可以试试用 `grep` 代替 `egrep` ，你会发现用 `grep` 不能得到正确的结果。你也可以通过管道把命令结果用 `less` 过滤器来查看。最终命令像这样：
|
||||
|
||||
```
|
||||
[student@studentvm1 testdir]$ for RPM in `rpm -qa | sort | uniq` ; do rpm -qi $RPM ; done | egrep -i "^Name|^Summary" > RPM-summary.txt
|
||||
```
|
||||
|
||||
这个命令行程序用到了管道、重定向和 `for` 循环，这些全都在一行中。它把你的 CLI 程序的结果重定向到了一个文件，这个文件可以在邮件中使用或在其他地方作为输入使用。
|
||||
|
||||
这个一次一步构建程序的过程让你能看到每步的结果，以此来确保整个程序以你期望的流程进行且输出你想要的结果。
|
||||
|
||||
白痴老板最终收到了超过 1900 个不同的 RPM 包的清单，我严重怀疑根本就没人读过这个列表。我给了他们想要的东西，没有从他们嘴里听到过任何关于 RPM 包的信息。
|
||||
|
||||
### 其他循环
|
||||
|
||||
Bash 中还有两种其他类型的循环结构：`while` 和 `until` 结构，两者在语法和功能上都类似。这些循环结构的基础语法很简单：
|
||||
|
||||
```
|
||||
while [ expression ] ; do list ; done
|
||||
```
|
||||
|
||||
逻辑解释：表达式（`expression`）结果为 true 时，执行程序语句 `list`。表达式结果为 false 时，退出循环。
|
||||
|
||||
```
|
||||
until [ expression ] ; do list ; done
|
||||
```
|
||||
|
||||
逻辑解释：执行程序语句 `list`，直到表达式的结果为 true。当表达式结果为 true 时，退出循环。
|
||||
|
||||
#### While 循环
|
||||
|
||||
`while` 循环用于当逻辑表达式结果为 true 时执行一系列程序语句。假设你的 PWD 仍是 `~/testdir`。
|
||||
|
||||
最简单的 `while` 循环形式是这个会一直运行下去的循环。下面格式的条件语句永远以 `true` 作为返回。你也可以用简单的 `1` 代替 `true`，结果一样，但是这解释了 true 表达式的用法。
|
||||
|
||||
```
|
||||
[student@studentvm1 testdir]$ X=0 ; while [ true ] ; do echo $X ; X=$((X+1)) ; done | head
|
||||
0
|
||||
1
|
||||
2
|
||||
3
|
||||
4
|
||||
5
|
||||
6
|
||||
7
|
||||
8
|
||||
9
|
||||
[student@studentvm1 testdir]$
|
||||
```
|
||||
|
||||
既然你已经学了 CLI 的各部分知识，那就让它变得更有用处。首先，为了防止变量 `$X` 在前面的程序或 CLI 命令执行后有遗留的值，设置 `$X` 的值为 0。然后，因为逻辑表达式 `[ true ]` 的结果永远是 1，即 true，在 `do` 和 `done` 中间的程序指令列表会一直执行 — 或者直到你按下 `Ctrl+C` 抑或发送一个 2 号信号给程序。那些程序指令是算数扩展，用来打印变量 `$X` 当前的值并加 1.
|
||||
|
||||
《[系统管理员的 Linux 哲学][5]》的信条之一是追求优雅，实现优雅的一种方式就是简化。你可以用操作符 `++` 来简化这个程序。在第一个例子中，变量当前的值被打印出来，然后变量的值增加了。可以在变量后加一个 `++` 来表示这个逻辑：
|
||||
|
||||
```
|
||||
[student@studentvm1 ~]$ X=0 ; while [ true ] ; do echo $((X++)) ; done | head
|
||||
0
|
||||
1
|
||||
2
|
||||
3
|
||||
4
|
||||
5
|
||||
6
|
||||
7
|
||||
8
|
||||
9
|
||||
```
|
||||
|
||||
现在删掉程序最后的 `| head` 再运行一次。
|
||||
|
||||
在下面这个版本中，变量在值被打印之前就自增了。这是通过在变量之前添加 `++` 操作符实现的。你能看出区别吗？
|
||||
|
||||
```
|
||||
[student@studentvm1 ~]$ X=0 ; while [ true ] ; do echo $((++X)) ; done | head
|
||||
1
|
||||
2
|
||||
3
|
||||
4
|
||||
5
|
||||
6
|
||||
7
|
||||
8
|
||||
9
|
||||
```
|
||||
|
||||
你已经把打印变量的值和自增简化到了一条语句。类似 `++` 操作符，也有 `--` 操作符。
|
||||
|
||||
你需要一个在循环到某个特定数字时终止循环的方法。把 true 表达式换成一个数字比较表达式来实现它。这里有一个循环到 5 终止的程序。在下面的示例代码中，你可以看到 `-le` 是 “小于或等于” 的数字逻辑操作符。整个语句的意思：只要 `$X` 的值小于或等于 5，循环就一直运行。当 `$X` 增加到 6 时，循环终止。
|
||||
|
||||
```
|
||||
[student@studentvm1 ~]$ X=0 ; while [ $X -le 5 ] ; do echo $((X++)) ; done
|
||||
0
|
||||
1
|
||||
2
|
||||
3
|
||||
4
|
||||
5
|
||||
[student@studentvm1 ~]$
|
||||
```
|
||||
|
||||
#### Until 循环
|
||||
|
||||
`until` 命令非常像 `while` 命令。不同之处是，它直到逻辑表达式的值是 `true` 之前，会一直循环。看一下这种结构最简单的格式：
|
||||
|
||||
```
|
||||
[student@studentvm1 ~]$ X=0 ; until false ; do echo $((X++)) ; done | head
|
||||
0
|
||||
1
|
||||
2
|
||||
3
|
||||
4
|
||||
5
|
||||
6
|
||||
7
|
||||
8
|
||||
9
|
||||
[student@studentvm1 ~]$
|
||||
```
|
||||
|
||||
它用一个逻辑比较表达式来计数到一个特定的值：
|
||||
|
||||
```
|
||||
[student@studentvm1 ~]$ X=0 ; until [ $X -eq 5 ] ; do echo $((X++)) ; done
|
||||
0
|
||||
1
|
||||
2
|
||||
3
|
||||
4
|
||||
[student@studentvm1 ~]$ X=0 ; until [ $X -eq 5 ] ; do echo $((++X)) ; done
|
||||
1
|
||||
2
|
||||
3
|
||||
4
|
||||
5
|
||||
[student@studentvm1 ~]$
|
||||
```
|
||||
|
||||
### 总结
|
||||
|
||||
本系列探讨了构建 Bash 命令行程序和 shell 脚本的很多强大的工具。但是这仅仅是你能用 Bash 做的很多有意思的事中的冰山一角，接下来就看你的了。
|
||||
|
||||
我发现学习 Bash 编程最好的方法就是实践。找一个需要多个 Bash 命令的简单项目然后写一个 CLI 程序。系统管理员们要做很多适合 CLI 编程的工作，因此我确信你很容易能找到自动化的任务。
|
||||
|
||||
很多年前，尽管我对其他的 Shell 语言和 Perl 很熟悉，但还是决定用 Bash 做所有系统管理员的自动化任务。我发现，有时稍微搜索一下，我可以用 Bash 实现我需要的所有事情。
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: https://opensource.com/article/19/10/programming-bash-loops
|
||||
|
||||
作者：[David Both][a]
|
||||
选题：[lujun9972][b]
|
||||
译者：[lxbwolf](https://github.com/lxbwolf)
|
||||
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/dboth
|
||||
[b]: https://github.com/lujun9972
|
||||
[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/fail_progress_cycle_momentum_arrow.png?itok=q-ZFa_Eh (arrows cycle symbol for failing faster)
|
||||
[2]: http://www.both.org/?page_id=1183
|
||||
[3]: https://linux.cn/article-11552-1.html
|
||||
[4]: https://linux.cn/article-11687-1.html
|
||||
[5]: https://www.apress.com/us/book/9781484237298
|
||||
@ -1,8 +1,8 @@
|
||||
[#]: collector: (lujun9972)
|
||||
[#]: translator: (geekpi)
|
||||
[#]: reviewer: ( )
|
||||
[#]: publisher: ( )
|
||||
[#]: url: ( )
|
||||
[#]: reviewer: (wxy)
|
||||
[#]: publisher: (wxy)
|
||||
[#]: url: (https://linux.cn/article-11716-1.html)
|
||||
[#]: subject: (Create virtual machines with Cockpit in Fedora)
|
||||
[#]: via: (https://fedoramagazine.org/create-virtual-machines-with-cockpit-in-fedora/)
|
||||
[#]: author: (Karlis KavacisPaul W. Frields https://fedoramagazine.org/author/karlisk/https://fedoramagazine.org/author/pfrields/)
|
||||
@ -12,19 +12,19 @@
|
||||
|
||||
![][1]
|
||||
|
||||
本文向你展示如何在 Fedora 31 上使用安装 Cockpit 所需软件来创建和管理虚拟机。Cockpit 是一个[交互式管理界面][2]，可让你在任何受支持的 Web 浏览器上访问和管理系统。随着 [virt-manager 正逐渐废弃][3]，用户被鼓励使用 Cockpit 来替换它。
|
||||
本文向你展示如何在 Fedora 31 上使用安装 Cockpit 所需软件来创建和管理虚拟机。Cockpit 是一个[交互式管理界面][2]，可让你在任何受支持的 Web 浏览器上访问和管理系统。随着 [virt-manager 逐渐被废弃][3]，鼓励用户使用 Cockpit 来替换它。
|
||||
|
||||
Cockpit 是一个积极开发的项目，它有许多扩展其工作的插件。例如，其中一个是 “Machines”，它与 libvirtd 交互并允许用户创建和管理虚拟机。
|
||||
Cockpit 是一个正在活跃开发的项目，它有许多扩展其工作的插件。例如，其中一个是 “Machines”，它与 libvirtd 交互并允许用户创建和管理虚拟机。
|
||||
|
||||
### 安装软件
|
||||
|
||||
先决所需软件是 _libvirt _、_ cockpit_ 和 _cockpit-machines_。要将它们安装在 Fedora 31 上，请在终端[使用 sudo][4] 运行以下命令：
|
||||
先决所需软件是 `libvirt`、`cockpit` 和 `cockpit-machines`。要将它们安装在 Fedora 31 上，请在终端[使用 sudo][4] 运行以下命令：
|
||||
|
||||
```
|
||||
$ sudo dnf install libvirt cockpit cockpit-machines
|
||||
```
|
||||
|
||||
Cockpit 也在 “Headless Management” 软件包组中。该组对于仅通过网络访问的基于 Fedora 的服务器很有用。在这里，请使用以下命令进行安装：
|
||||
Cockpit 也在 “Headless Management” 软件包组中。该软件组对于仅通过网络访问的基于 Fedora 的服务器很有用。在这里，请使用以下命令进行安装：
|
||||
|
||||
```
|
||||
$ sudo dnf groupinstall "Headless Management"
|
||||
@ -32,7 +32,7 @@ $ sudo dnf groupinstall "Headless Management"
|
||||
|
||||
### 设置 Cockpit 服务
|
||||
|
||||
安装了必要的软件包后，就该启用服务了。 _libvirtd_ 服务运行虚拟机，而 Cockpit 有一个激活的套接字服务，可让你访问 Web GUI：
|
||||
安装了必要的软件包后，就该启用服务了。`libvirtd` 服务运行虚拟机，而 Cockpit 有一个激活的套接字服务，可让你访问 Web GUI：
|
||||
|
||||
```
|
||||
$ sudo systemctl enable libvirtd --now
|
||||
@ -59,35 +59,31 @@ $ sudo systemctl status cockpit.socket
|
||||
|
||||
使用系统的用户名和密码登录界面。你还可以选择是否允许在此会话中将密码用于管理任务。
|
||||
|
||||
选择 _Virtual Machines_，然后选择_ Create VM_ 来创建一台新的虚拟机。控制台为你提供几个选项：
|
||||
选择 “Virtual Machines”，然后选择 “Create VM” 来创建一台新的虚拟机。控制台为你提供几个选项：
|
||||
|
||||
* 使用 Cockpit 的内置库下载操作系统
|
||||
* 使用系统上已下载的安装媒体
|
||||
* 指向系统安装树的 URL
|
||||
* 通过 [PXE][5] 协议通过网络引导媒体
|
||||
|
||||
|
||||
|
||||
输入所有必要的参数。然后选择 _Create_ 启动新虚拟机。
|
||||
输入所有必要的参数。然后选择 “Create” 启动新虚拟机。
|
||||
|
||||
此时，将出现一个图形控制台。大多数现代 Web 浏览器都允许你使用键盘和鼠标与 VM 控制台进行交互。现在，你可以完成安装并使用新的 VM，就像[过去通过 virt-manager][6] 一样。
|
||||
|
||||
* * *
|
||||
|
||||
_照片由 [Miguel Teixeira][7] 发布于 [Flickr][8]（CC BY-SA 2.0）_
|
||||
*照片由 [Miguel Teixeira][7] 发布于 [Flickr][8]（CC BY-SA 2.0）*
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: https://fedoramagazine.org/create-virtual-machines-with-cockpit-in-fedora/
|
||||
|
||||
作者：[Karlis KavacisPaul W. Frields][a]
|
||||
作者：[Karlis Kavacis][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)
|
||||
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://fedoramagazine.org/author/karlisk/https://fedoramagazine.org/author/pfrields/
|
||||
[a]: https://fedoramagazine.org/author/karlisk/
|
||||
[b]: https://github.com/lujun9972
|
||||
[1]: https://fedoramagazine.org/wp-content/uploads/2019/11/create-vm-cockpit-816x345.jpg
|
||||
[2]: https://cockpit-project.org/
|
||||
@ -0,0 +1,112 @@
|
||||
[#]: collector: (lujun9972)
|
||||
[#]: translator: ( )
|
||||
[#]: reviewer: ( )
|
||||
[#]: publisher: ( )
|
||||
[#]: url: ( )
|
||||
[#]: subject: (Darktable 3 Released With GUI Rework and New Features)
|
||||
[#]: via: (https://itsfoss.com/darktable-3-release/)
|
||||
[#]: author: (Abhishek Prakash https://itsfoss.com/author/abhishek/)
|
||||
|
||||
Darktable 3 Released With GUI Rework and New Features
|
||||
======
|
||||
|
||||
Here’s the Christmas gift for the photography enthusiasts. Darktable 3.0 has just released.
|
||||
|
||||
[Darktable][1] is one of the [best applications for editing RAW images on Linux][2]. You can consider it as a [free and open source alternative to Adobe Lightroom][3].
|
||||
|
||||
Darktable 3 is a major new release with tons of feature improvements and a complete rework of the user interface. The GUI is now completely controlled by GTK+ CSS rules, which makes the whole GUI themable. There are eight themes available by default.
|
||||
|
||||
With the help of over 3000 commits and 553 pull requests, the new release has fixed 66 bugs and added many new features.
|
||||
|
||||
Let’s see what features this new release brings.
|
||||
|
||||
### New features in Darktable 3.0
|
||||
|
||||
![Darktable 3.0 Screenshot][4]
|
||||
|
||||
Here are the highlighted new features:
|
||||
|
||||
* Reworked UI
|
||||
* A new module for handling 3D RGB Lut transformations
|
||||
* Many improvements to the ‘denoise (profiled)’ module
|
||||
* A new ‘culling’ mode and timeline view added
|
||||
* Many improvements to the ‘denoise (profiled)’ module
|
||||
* New tone equalizer’ basic and filmic RGB modules
|
||||
* Better 4K/5K display support
|
||||
* Undo/redo support for more operations
|
||||
* Many code optimizations for CPU and SSE paths
|
||||
* Support for exporting to Google Photos
|
||||
* More camera support, white balance presets, and noise profiles
|
||||
* Plenty of bug fixes and feature improvements
|
||||
|
||||
|
||||
|
||||
You can read about all the changes in the [release notes on GitHub][5].
|
||||
|
||||
### Installing Darktable 3.0 on Linux
|
||||
|
||||
Let’s see how to get the latest Darktable release.
|
||||
|
||||
#### Installing Darktable 3.0 on Ubuntu-based distributions
|
||||
|
||||
Darktable is available in Ubuntu but you won’t get the latest release immediately. For the LTS version, it may take months before you have this version update.
|
||||
|
||||
Worry not! Darktable provides its [own PPA][6] to install the latest release on Ubuntu-based distributions.
|
||||
|
||||
Unfortuntaley, That Darktable PPA has not been updated with the new release.
|
||||
|
||||
Worry not (again)! Thanks to our friend [Ji M of Ubuntu Handbook][7], we have an unofficial PPA for easily installing Darktable 3.0 on Ubuntu and other Ubuntu based distributions.
|
||||
|
||||
Open a terminal and use these commands one by one:
|
||||
|
||||
```
|
||||
sudo add-apt-repository ppa:ubuntuhandbook1/darktable
|
||||
sudo apt update
|
||||
sudo apt install darktable
|
||||
```
|
||||
|
||||
#### Uninstall Darktable 3
|
||||
|
||||
To remove Darktable installed via this PPA, you can first uninstall the application:
|
||||
|
||||
```
|
||||
sudo apt remove darktable
|
||||
```
|
||||
|
||||
And then [remove the PPA][8] as well:
|
||||
|
||||
```
|
||||
sudo add-apt-repository -r ppa:ubuntuhandbook1/darktable
|
||||
```
|
||||
|
||||
#### Installing Darktable on other Linux distributions
|
||||
|
||||
You may wait for your distribution to provide this new release through the software manager.
|
||||
|
||||
You may also download the tarball or the entire source code from the GitHub release page (it’s at the bottom of the page).
|
||||
|
||||
[Download Darktable 3.0][5]
|
||||
|
||||
With Darktable 3, you can edit your holiday pictures better :)
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: https://itsfoss.com/darktable-3-release/
|
||||
|
||||
作者：[Abhishek Prakash][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://itsfoss.com/author/abhishek/
|
||||
[b]: https://github.com/lujun9972
|
||||
[1]: https://www.darktable.org/
|
||||
[2]: https://itsfoss.com/raw-image-tools-linux/
|
||||
[3]: https://itsfoss.com/open-source-photoshop-alternatives/
|
||||
[4]: https://i1.wp.com/itsfoss.com/wp-content/uploads/2019/12/darktable_3_screenshot.jpg?ssl=1
|
||||
[5]: https://github.com/darktable-org/darktable/releases/tag/release-3.0.0
|
||||
[6]: https://launchpad.net/~pmjdebruijn/+archive/ubuntu/darktable-release
|
||||
[7]: http://ubuntuhandbook.org/index.php/2019/12/install-darktable-3-0-0-ubuntu-18-04-19-10/
|
||||
[8]: https://itsfoss.com/how-to-remove-or-delete-ppas-quick-tip/
|
||||
@ -0,0 +1,63 @@
|
||||
[#]: collector: (lujun9972)
|
||||
[#]: translator: ( )
|
||||
[#]: reviewer: ( )
|
||||
[#]: publisher: ( )
|
||||
[#]: url: ( )
|
||||
[#]: subject: (How to run a business with open source: Top reads)
|
||||
[#]: via: (https://opensource.com/article/19/12/business-open-source)
|
||||
[#]: author: (Jim Hall https://opensource.com/users/jim-hall)
|
||||
|
||||
How to run a business with open source: Top reads
|
||||
======
|
||||
Open source software is open for business, as evidenced in the these top
|
||||
5 articles from 2019.
|
||||
![Open for business][1]
|
||||
|
||||
Open source is ready to get to work, and in 2019, Opensource.com had many great articles about how organizations have adopted open source software or open methods to drive their business. As open source matures, we've seen open source not just replace proprietary software, but create entirely new business models.
|
||||
|
||||
Check out this list of five outstanding articles from Opensource.com in 2019 about running a business with open source.
|
||||
|
||||
### Get your business up and running with these open source tools
|
||||
|
||||
In [_Get your business up and running with these open source tools_][2], I explain: "Yes, you really can operate a business using open source software." In this article, I review the key open source software tools that I use to run my company, including Inkscape, GIMP, LibreOffice, and Scribus.
|
||||
|
||||
### What's your favorite open source BI software?
|
||||
|
||||
As Lauren Maffeo explains in _[What's your favorite open source BI software?][3]_ "Open source business intelligence (BI) software helps users upload, visualize, and make decisions based on data that is pulled from several sources... BI involves turning data into insights that help your business make better decisions... Before choosing which open source BI tool to adopt, it's worth weighing the pros and cons of each tool against your business needs." The article's accompanying poll asks readers whether they prefer Pentaho, Logz.io, Cluvio, Qlikview, Sisense, or another BI application. Answer the poll to let us know which is your favorite and to see what other readers say.
|
||||
|
||||
### Scrum vs. kanban: Which agile framework is better?
|
||||
|
||||
Because scrum and kanban both fall under the agile framework umbrella, many people confuse them or think they're the same thing. There are differences, however. In [_Scrum vs. kanban: Which agile framework is better?_][4] Taz Brown explains the differences between scrum and kanban and helps you decide which one may be best for your team.
|
||||
|
||||
### What is Small Scale Scrum?
|
||||
|
||||
"Agile is fast becoming a mainstream way industries act, behave, and work as they look to improve efficiency, minimize costs, and empower staff. Most software developers naturally think, act, and work this way, and alignment towards agile software methodologies has gathered pace in recent years," write Agnieszka Gancarczyk and Leigh Griffin in [_What is Small Scale Scrum?_][5] In this article, they explain how the scrum agile methodology can help small teams work more efficiently.
|
||||
|
||||
### What does DevOps mean to you?
|
||||
|
||||
In *[What does DevOps mean to you?][6] *Girish Managoli offers one answer to this article's headline: "DevOps is a process of software development focusing on communication and collaboration to facilitate rapid application and product deployment." But there are a range of opinions and expectations around DevOps. To help explain DevOps and how to leverage it in organizations, Girish interviewed six experts to break down DevOps and the key practices and philosophies in making DevOps work for you.
|
||||
|
||||
### Open source is open for business
|
||||
|
||||
As open source plays an increasingly important role in business, there's more to learn about the topic. What do you want to know about it in 2020? Please share your ideas for articles in the comments—or even share your own experiences with running a business on open source software by [writing an article for Opensource.com][7].
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: https://opensource.com/article/19/12/business-open-source
|
||||
|
||||
作者：[Jim Hall][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/jim-hall
|
||||
[b]: https://github.com/lujun9972
|
||||
[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/BUSINESS_openseries.png?itok=rCtTDz5G (Open for business)
|
||||
[2]: https://opensource.com/article/19/9/business-creators-open-source-tools
|
||||
[3]: https://opensource.com/article/19/8/favorite-open-source-bi-software
|
||||
[4]: https://opensource.com/article/19/8/scrum-vs-kanban
|
||||
[5]: https://opensource.com/article/19/1/what-small-scale-scrum
|
||||
[6]: https://opensource.com/article/19/1/what-does-devops-mean-you
|
||||
[7]: https://opensource.com/how-submit-article
|
||||
@ -1,3 +1,4 @@
|
||||
chenmu-kk is translating.
|
||||
How the four components of a distributed tracing system work together
|
||||
======
|
||||
|
||||
|
||||
@ -1,5 +1,5 @@
|
||||
[#]: collector: (lujun9972)
|
||||
[#]: translator: ( )
|
||||
[#]: translator: (chen-ni)
|
||||
[#]: reviewer: ( )
|
||||
[#]: publisher: ( )
|
||||
[#]: url: ( )
|
||||
@ -144,7 +144,7 @@ via: https://opensource.com/article/19/7/how-make-old-computer-useful-again
|
||||
|
||||
作者：[Howard Fosdick][a]
|
||||
选题：[lujun9972][b]
|
||||
译者：[译者ID](https://github.com/译者ID)
|
||||
译者：[译者ID](https://github.com/chen-ni)
|
||||
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
|
||||
|
||||
@ -1,72 +0,0 @@
|
||||
[#]: collector: (lujun9972)
|
||||
[#]: translator: (geekpi)
|
||||
[#]: reviewer: ( )
|
||||
[#]: publisher: ( )
|
||||
[#]: url: ( )
|
||||
[#]: subject: (Customize your Linux desktop with KDE Plasma)
|
||||
[#]: via: (https://opensource.com/article/19/12/linux-kde-plasma)
|
||||
[#]: author: (Seth Kenlon https://opensource.com/users/seth)
|
||||
|
||||
Customize your Linux desktop with KDE Plasma
|
||||
======
|
||||
This article is part of a special series of 24 days of Linux desktops.
|
||||
If you think there's no such thing as too much opportunity to customize
|
||||
your desktop, KDE Plasma may be for you.
|
||||
![5 pengiuns floating on iceburg][1]
|
||||
|
||||
The Plasma desktop by the KDE community is a pinnacle among open source desktops. KDE got into the Linux desktop market early, but since its foundational Qt toolkit did not have a fully open license at the time, the [GNOME][2] desktop was created. Since then, Qt has become open source, and KDE (and its derivatives, like the [Trinity desktop][3]) has thrived.
|
||||
|
||||
You may find the KDE desktop in your distribution's software repository, or you can download and install a distribution that ships KDE as its default. Before you install, be aware that KDE provides a full, integrated, and robust desktop experience, so several KDE applications are installed along with it. If you're already running a different desktop, you will find yourself with redundant applications (two PDF readers, several media players, two or more file managers, and so on). If you just want to try the KDE desktop without committing to it, you can install a KDE-based distribution in a virtual machine, such as [GNOME Boxes][4], or you can try a bootable OS like [Porteus][5].
|
||||
|
||||
### KDE desktop tour
|
||||
|
||||
The [KDE Plasma][6] desktop is relatively boring at first glance—but in a comforting way. It's got the industry-standard layout: pop-up application menu in the bottom-left corner, taskbar in the middle, system tray on the right. It's exactly what you'd expect from a standard household or business computer.
|
||||
|
||||
![KDE Plasma desktop][7]
|
||||
|
||||
What sets KDE apart, though, is that you can change nearly anything you want. The Qt toolkit can be taken apart and rearranged in some surprising ways, meaning you can essentially design your own desktop using KDE's parts as your foundation. The settings available for how your desktop behaves are vast, too. KDE can act as a standard desktop, a tiling window manager, and anything in between. You can create your own window rules by window class, role, type, title, or any combination thereof, so if you want specific applications to behave differently than everything else, you can create an exception to global settings.
|
||||
|
||||
Furthermore, there's a rich collection of widgets to enable you to customize the way you interface with your desktop. There's a GNOME-like full-screen application launcher, a Unity-like dock launcher and icons-only taskbar, and a traditional taskbar. You can create and place panels on any edge of the screen you want.
|
||||
|
||||
![A slightly customized KDE desktop][8]
|
||||
|
||||
There's so much customization, in fact, that one of the most common critiques of KDE is that it's _too customizable_, so keep in mind that customization is optional. You can use the Plasma desktop in its default configuration, and change things gradually and only as you feel necessary. What matters most about Plasma desktop configuration options isn't their number, but that they're discoverable and intuitive, either in the System Settings application or with a right-click.
|
||||
|
||||
The fact is, on KDE, there's almost never just one way to accomplish any given task, and its users see that as its greatest strength. There's no implied workflow in KDE, only a default. And all defaults can be changed, until everything you need to do with your desktop is second-nature.
|
||||
|
||||
### Consistency and integration
|
||||
|
||||
The KDE community prides itself on consistency and integration, made possible through great developer and community management and the KDE libraries. The developers of KDE aren't just developers of a desktop. They provide a [stunning collection of applications][9], each of them created with KDE libs that extend and standardize common Qt widgets. It's no accident that after using KDE for a few months, whether you open [DigiKam][10] for photo management or Kmail to check email or KTorrent to grab the latest ISO or Dolphin to manage files, your muscle memory takes you where you need to go in the UI before you consciously think about it.
|
||||
|
||||
![KDE on Porteus][11]
|
||||
|
||||
### Try KDE
|
||||
|
||||
KDE has something for everyone. Use its default settings for a smooth, plain-vanilla desktop experience, or customize it to make it your own. It's a stable, attractive, and robust desktop environment that probably has everything you need for whatever you want to do on Linux.
|
||||
|
||||
KDE originally stood for Kool Desktop Environment, but is now known by many as the K Desktop...
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: https://opensource.com/article/19/12/linux-kde-plasma
|
||||
|
||||
作者：[Seth Kenlon][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/seth
|
||||
[b]: https://github.com/lujun9972
|
||||
[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/rh_003499_01_linux31x_cc.png?itok=Pvim4U-B (5 pengiuns floating on iceburg)
|
||||
[2]: https://opensource.com/article/19/12/gnome-linux-desktop
|
||||
[3]: https://opensource.com/article/19/12/linux-trinity-desktop-environment-tde
|
||||
[4]: https://opensource.com/article/19/5/getting-started-gnome-boxes-virtualization
|
||||
[5]: https://opensource.com/article/19/6/linux-distros-to-try
|
||||
[6]: https://kde.org/plasma-desktop
|
||||
[7]: https://opensource.com/sites/default/files/uploads/advent-kde-presskit.jpg (KDE Plasma desktop)
|
||||
[8]: https://opensource.com/sites/default/files/uploads/advent-kde-dock.jpg (A slightly customized KDE desktop)
|
||||
[9]: https://kde.org/applications/
|
||||
[10]: https://opensource.com/life/16/5/how-use-digikam-photo-management
|
||||
[11]: https://opensource.com/sites/default/files/uploads/advent-kde.jpg (KDE on Porteus)
|
||||
@ -0,0 +1,97 @@
|
||||
[#]: collector: (lujun9972)
|
||||
[#]: translator: ( )
|
||||
[#]: reviewer: ( )
|
||||
[#]: publisher: ( )
|
||||
[#]: url: ( )
|
||||
[#]: subject: (12 open source resources for kids and young adults)
|
||||
[#]: via: (https://opensource.com/article/19/12/kids-students-education)
|
||||
[#]: author: (Don Watkins https://opensource.com/users/don-watkins)
|
||||
|
||||
12 open source resources for kids and young adults
|
||||
======
|
||||
Explore new technologies with Opensource.com's top 12 articles from 2019
|
||||
about learning an open source technology.
|
||||
![Person reading a book and digital copy][1]
|
||||
|
||||
Are you looking to challenge your children (or even yourself) to learn new things about open source technologies? Whether you're in elementary school, high school, or college, or even a parent or teacher, Opensource.com has some great reading about open source technologies suitable for the younger generation. Here are our top 12 articles from 2019 on open source for students (and those who love them).
|
||||
|
||||
### Hacking math education with Python
|
||||
|
||||
As a student, I had difficulty with the abstraction of mathematics. Traditional classroom instruction didn't work for me. Peter Farrell has another approach for learners who are challenged by conventional mathematics instruction. His unique approach, which teaches math using Python, resonated with me when I interviewed him about how he is [_Hacking math education with Python_][2].
|
||||
|
||||
### 5 open source tools for teaching young children to read
|
||||
|
||||
No doubt, you have seen how easy it is for children to master today's electronic devices—but what about traditional literacy? Are today's children getting the foundation in reading, writing, and arithmetic that they need to be successful? Laura Janusek's [_5 open source tools for teaching young children to read_][3] may help. She says, "Access to literary environments has been shown to impact literacy and attitudes towards reading. Why not strive to create a digital literacy environment for our kids by filling our devices with educational technologies, just like our shelves are filled with books?"
|
||||
|
||||
### What programming language would you teach a kid first?
|
||||
|
||||
Coding has become a hot area for schools and parents. Opinions abound on the best computer language to teach and when to begin teaching it. Lauren Pritchett celebrated Ada Lovelace Day 2019 by exploring [_What programming language would you teach kids first?_][4] Be sure to take the accompanying poll, too.
|
||||
|
||||
### Getting started with the BBC Microbit
|
||||
|
||||
Learning to code should be fun, and one of the ways to ensure a great early experience is by using an inexpensive open hardware board. In [_Getting started with the BBC Microbit_][5], I provide step-by-step directions and some code examples so your child can learn to program with MicroPython.
|
||||
|
||||
### Introducing kids to computational thinking with Python
|
||||
|
||||
Coding can be the key that lifts children out of poverty and empowers them to gain new skills, confidence, and the knowledge necessary to break free from socioeconomic disadvantages. In [_Introducing kids to computational thinking with Python_][6], I interviewed librarian Qumisha Goss, who is leveraging the power of Python to transform children's lives in Detroit.
|
||||
|
||||
### A dozen ways to learn Python
|
||||
|
||||
Do you know someone who really wants to learn to Python but is looking for the right hook to get started? Removing abstraction has been key to my best learning experiences, and I share some of the resources I've found in [_A dozen ways to learn Python_][7]. They will start you on your journey to Python proficiency and sustain your learning over the long haul.
|
||||
|
||||
### 100 ways to learn Python and R for data science
|
||||
|
||||
Many people want to learn data science but are drowning in the deluge of information available online, leaving them confused about where to find the best book, tutorial, or other learning resources. Where would you turn to learn the skills necessary to play a role in this rapidly growing field? Chris Englehardt, Dorris Scott, and Annu Singh share their suggestions in [_100 ways to learn Python and_ _R for data science_][8].
|
||||
|
||||
### How a trip to China inspired Endless OS and teaching kids to hack
|
||||
|
||||
I've long been interested in inexpensive, Linux-based computers that help children around the world learn how to code. One of these is Endless' Hack, a low-cost laptop, and an accompanying series of video games designed to get kids coding and become creative problem solvers while they're having fun. In 2019, I got to interview Endless' founder Matt Dalio, where he shares [_How a trip to China inspired Endless OS and teaching kids to hack_][9].
|
||||
|
||||
### How to use the internet to learn IT skills
|
||||
|
||||
Looking to do something meaningful in the new year? How about helping a few young people take their first steps in an IT career? You can follow the lead of David Clinton, a systems administrator, teacher, and writer, who shares [_How to use the internet to learn IT skills_][10]. Giving students access to open source tools and letting them explore and iterate creates a rich learning experience, he explains.
|
||||
|
||||
### Digital divide? How the Asian Penguins share Linux at Minnesota charter school
|
||||
|
||||
Stu Keroff is an educator who has turned his passion for Linux and open source into a school–community outreach program that serves a large number of immigrant families in Minnesota. He is a husband, father, teacher, speaker, and advocate for Linux in K-12 education and a winner of the [2016 Opensource.com Readers Choice Award][11]. In [_Digital divide? How the Asian Penguins share Linux at Minnesota charter school_][12], Stu shares his Linux-powered solution to expand digital literacy in his community.
|
||||
|
||||
### 13 books for picking up new tech in 2019
|
||||
|
||||
If you (or someone you know) learn best by reading, my [_13 books for picking up new tech in 2019_][13] may help you discover a new skill that piques your curiosity. The list includes books on everything from Python to Linux to developing games on a Raspberry Pi.
|
||||
|
||||
### 11 surprising ways you use Linux every day
|
||||
|
||||
If you, like me, wonder what powers all the electronic gadgets that power our day-to-day lives today, read my article on [_11 surprising ways you use Linux every day_][14]. You might be amazed at how much we depend on open source to get us through our days.
|
||||
|
||||
### A lifetime of learning
|
||||
|
||||
What would you like to know to help the children in your life expand their tech knowledge and skills? Please share your ideas in the comments, or even consider sharing your own experiences with Opensource.com readers by [submitting an article][15] about your favorite open source education topic.
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: https://opensource.com/article/19/12/kids-students-education
|
||||
|
||||
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/read_book_guide_tutorial_teacher_student_apaper.png?itok=_GOufk6N (Person reading a book and digital copy)
|
||||
[2]: https://opensource.com/article/19/1/hacking-math
|
||||
[3]: https://opensource.com/article/19/4/early-literacy-tools
|
||||
[4]: https://opensource.com/article/19/10/first-programming-language-kids
|
||||
[5]: https://opensource.com/article/19/8/getting-started-bbc-microbit
|
||||
[6]: https://opensource.com/article/19/2/break-down-stereotypes-python
|
||||
[7]: https://opensource.com/article/19/8/dozen-ways-learn-python
|
||||
[8]: https://opensource.com/article/19/5/learn-python-r-data-science
|
||||
[9]: https://opensource.com/article/19/6/endless-digital-literacy
|
||||
[10]: https://opensource.com/article/19/5/it-skills-internet
|
||||
[11]: https://opensource.com/community/16/2/winners-2016-community-awards
|
||||
[12]: https://opensource.com/article/19/2/asian-penguins-close-digital-divide
|
||||
[13]: https://opensource.com/article/19/1/tech-books-new-skils
|
||||
[14]: https://opensource.com/article/19/8/everyday-tech-runs-linux
|
||||
[15]: https://opensource.com/how-submit-article
|
||||
84
sources/tech/20191225 5 security tips from Santa.md
Normal file
84
sources/tech/20191225 5 security tips from Santa.md
Normal file
@ -0,0 +1,84 @@
|
||||
[#]: collector: (lujun9972)
|
||||
[#]: translator: ( )
|
||||
[#]: reviewer: ( )
|
||||
[#]: publisher: ( )
|
||||
[#]: url: ( )
|
||||
[#]: subject: (5 security tips from Santa)
|
||||
[#]: via: (https://opensource.com/article/19/12/security-tips)
|
||||
[#]: author: (Mike Bursell https://opensource.com/users/mikecamel)
|
||||
|
||||
5 security tips from Santa
|
||||
======
|
||||
Stay off Santa's (and your employer's) naughty list by following this
|
||||
list of useful security tips and practices.
|
||||
![Security monster][1]
|
||||
|
||||
If you're reading this in 2019, it's almost Christmas (as celebrated according to the Western Christian calendar), and, like all children and IT professionals, it's time to write your letter to Santa/St. Nick/Father Christmas. Don't forget: those who have been good get nice presents and those who haven't get coal. Coal is _not_ a clean-burning fuel, and with climate change well and truly upon us,[1][2] you don't want to be going for the latter option.
|
||||
|
||||
Think back to all of the good security practices you've adopted over the past 11 or so months. And then think back to all of the bad security practices you've adopted when you should have been doing the _right_ thing. Oh, dear. It's not looking good for you, is it?
|
||||
|
||||
Here's the good news, though: because Santa is a benevolent soul, there's time to make amends (unless you're reading this after Christmas[2][3]). Here's a list of useful security tips and practices that Santa follows and therefore are bound to put you on his "good" side.
|
||||
|
||||
### 1\. Use a password manager
|
||||
|
||||
Santa is very careful with his passwords. Here's a little secret: from time to time, rather than have his elves handcraft every little present, he sources his gifts from other parties. I'm not suggesting that he pays market rates (he's ordering in bulk, and he has a very, very good credit rating), but he uses lots of different suppliers, and he's aware that not all of them take security as seriously as he does. He doesn't want all his account logins to be leaked if one of his suppliers is hacked, so he uses separate passwords for each account. Now, Santa, being Santa, could remember all of these details if he wanted to—and even generate unique passwords that meet all the relevant complexity requirements for each site—but he uses an open source [password manager][4] for safety and for succession planning.[3][5]
|
||||
|
||||
### 2\. Manage personal information properly
|
||||
|
||||
You may work for a large company, organisation, or government, and you may think you have lots of customers and associated data, but consider Santa. He manages (or has managed) names, birth dates, addresses, hobbies, shoe sizes, colour preferences, and other personal data for literally every person on Earth. That's an awful lot of sensitive data, and it needs to be protected. When people grow too old for presents from Santa,[4][6] he needs to delete their data securely. In fact, Santa may well be the archetypal [GDPR][7] data controller, and he needs to be very careful who and what can access the data that he holds. Of course, he encrypts all the data and is very careful about key management. He's also very aware of the dangers associated with cold boot attacks (given the average temperature around his residence), so he ensures data is properly wiped before shutdown.
|
||||
|
||||
### 3\. Measure and mitigate risk
|
||||
|
||||
Santa knows all about [risk][8]. He has complex systems for ordering, fulfillment, travel planning, logistics, and delivery that are the envy of most of the world. He understands what impact failure in any part of the supply chain can have on his customers: mainly children and IT professionals. He quantifies risk, recalculating it on a regular basis to ensure that he is up to date with possible vulnerabilities and ready with mitigations.
|
||||
|
||||
### 4\. Patch frequently but carefully
|
||||
|
||||
Santa absolutely cannot afford for his systems to go down, particularly around his most busy period. He has established processes to ensure that the [concerns of security are balanced with the needs of the business][9].[5][10] He knows that sometimes business continuity must take priority, and on other occasions, the impact of a security breach would be so major that patches just _have_ to be applied. He tells people what he wants and listens to their views, taking them into account where he can. In other words, he embraces open management, delegating decisions where possible to the people who are best positioned to make the call, and only intervenes when asked for an executive decision or when exceptions arise. Santa is a _very_ enlightened manager.
|
||||
|
||||
### 5\. Embrace diversity
|
||||
|
||||
One of the useful consequences of running a global operation is that Santa values diversity. Old or young (at heart); male, female, or gender-neutral; neurotypical or neurodiverse; of any culture, sexuality, race, ability, creed, or nose colour, Santa takes into account his stakeholders and their views on what might go wrong. What a fantastic set of viewpoints Santa has available to him! And he's surprisingly hip to the opportunities for security practices that a wide and [diverse set of opinions and experiences][11] can bring[6][12] not to mention the multiple [positive impacts][13] on his organisation.
|
||||
|
||||
### Summary
|
||||
|
||||
Here's my advice: Be like Santa, and adopt at least some of his security practices. You'll have a much better opportunity of getting onto his good side, and that's going to go down well—not just with him, but also with your employer, who is just certain to give you a nice bonus, right? And if not, well, it's not too late to write that letter directly to Santa himself.
|
||||
|
||||
* * *
|
||||
|
||||
1. If you have a problem with this statement, then either you need to find another article, or you're reading this in the far future where all our climate problems have been solved. I hope.
|
||||
2. Or you dwell in one of those cultures where Santa visits quite early in December.
|
||||
3. A high-flying goose in the face can do terrible damage to a fast-moving reindeer, and if the sleigh were to crash, what then...?
|
||||
4. Not me!
|
||||
5. Santa doesn't refer to it as a "business," but he's happy for us to call it that, so we can model our own experience on his. He's nice like that.
|
||||
6. Though Santa would never use the phrase "hip to the opportunities." He's way too cool for that.
|
||||
|
||||
|
||||
|
||||
Download the free All Things Open interview series eBook Jessica McKellar is an entrepreneur,...
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: https://opensource.com/article/19/12/security-tips
|
||||
|
||||
作者：[Mike Bursell][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/mikecamel
|
||||
[b]: https://github.com/lujun9972
|
||||
[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/security_password_chaos_engineer_monster.png?itok=J31aRccu (Security monster)
|
||||
[2]: tmp.PgLkHLx1Uz#1
|
||||
[3]: tmp.PgLkHLx1Uz#2
|
||||
[4]: https://opensource.com/article/18/4/3-password-managers-linux-command-line
|
||||
[5]: tmp.PgLkHLx1Uz#3
|
||||
[6]: tmp.PgLkHLx1Uz#4
|
||||
[7]: https://opensource.com/article/18/1/being-open-about-data-privacy
|
||||
[8]: http://aliceevebob.com/2019/03/12/dont-talk-security-talk-risk/
|
||||
[9]: http://aliceevebob.com/2017/10/17/stop-reading-start-patching/
|
||||
[10]: tmp.PgLkHLx1Uz#5
|
||||
[11]: http://aliceevebob.com/2017/08/08/diversity-in-it-security-not-just-a-canine-issue/
|
||||
[12]: tmp.PgLkHLx1Uz#6
|
||||
[13]: https://opensource.com/article/19/11/diversity-and-inclusion-strategies
|
||||
@ -0,0 +1,61 @@
|
||||
[#]: collector: (lujun9972)
|
||||
[#]: translator: ( )
|
||||
[#]: reviewer: ( )
|
||||
[#]: publisher: ( )
|
||||
[#]: url: ( )
|
||||
[#]: subject: (Making trade-offs when writing Python code)
|
||||
[#]: via: (https://opensource.com/article/19/12/zen-python-trade-offs)
|
||||
[#]: author: (Moshe Zadka https://opensource.com/users/moshez)
|
||||
|
||||
Making trade-offs when writing Python code
|
||||
======
|
||||
This is part of a special series about the Zen of Python focusing on the
|
||||
seventh, eighth, and ninth principles: readability, special cases, and
|
||||
practicality.
|
||||
![Brick wall between two people, a developer and an operations manager][1]
|
||||
|
||||
Software development is a discipline rife with trade-offs. For every choice, there is an equally defensible but opposite choice. Make a method private? You're encouraging copy-paste. Make a method public? You're committing prematurely to an interface.
|
||||
|
||||
Software developers make hard choices every minute. While all the principles in the [Zen of Python][2] cover trade-offs to some extent, the following principles take the hardest, coldest look at some trade-offs.
|
||||
|
||||
### Readability counts.
|
||||
|
||||
In some sense, this middle principle is indeed the center of the entire Zen of Python. The Zen is not about writing efficient programs. It is not even about writing robust programs, for the most part. It is about writing programs that _other people can read_.
|
||||
|
||||
Reading code, by its nature, happens after the code has been added to the system. Often, it happens long after. Neglecting readability is the easiest choice since it does not hurt right now. Whatever the reason for adding new code—a painful bug or a highly requested feature—it does hurt. Right now.
|
||||
|
||||
In the face of immense pressure to throw readability to the side and just "solve the problem," the Zen of Python reminds us: readability counts. Writing the code so it can be read is a form of compassion for yourself and others.
|
||||
|
||||
### Special cases aren't special enough to break the rules.
|
||||
|
||||
There is always an excuse. This bug is particularly painful; let's not worry about simplicity. This feature is particularly urgent; let's not worry about beauty. The domain rules covering this case are particularly hairy; let's not worry about nesting levels.
|
||||
|
||||
Once we allow special pleading, the dam wall breaks, and there are no more principles; things devolve into a Mad Max dystopia with every programmer for themselves, trying to find the best excuses.
|
||||
|
||||
Discipline requires commitment. It is only when things are hard, when there is a strong temptation, that a software developer is tested. There is always a valid excuse to break the rules, and that's why the rules must be kept the rules. Discipline is the art of saying no to exceptions. No amount of explanation can change that.
|
||||
|
||||
### Although, practicality beats purity.
|
||||
|
||||
> "If you think only of hitting, springing, striking, or touching the enemy, you will not be able actually to cut him."
|
||||
> — Miyamoto Musashi, _[The Book of Water][3]_
|
||||
|
||||
Ultimately, software development is a practical discipline. Its goal is to solve real problems, faced by real people. Practicality beats purity: above all else, we must _solve the problem_. If we think only about readability, simplicity, or beauty, we will not be able to actually _solve the problem_.
|
||||
|
||||
As Musashi suggested, the primary goal of every code change should be to _solve a problem_. The problem must be foremost in our minds. If we waver from it and think only of the Zen of Python, we have failed the Zen of Python. This is another one of those contradictions inherent in the Zen of Python.
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: https://opensource.com/article/19/12/zen-python-trade-offs
|
||||
|
||||
作者：[Moshe Zadka][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/moshez
|
||||
[b]: https://github.com/lujun9972
|
||||
[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/devops_confusion_wall_questions.png?itok=zLS7K2JG (Brick wall between two people, a developer and an operations manager)
|
||||
[2]: https://www.python.org/dev/peps/pep-0020/
|
||||
[3]: https://en.wikipedia.org/wiki/The_Book_of_Five_Rings#The_Book_of_Water
|
||||
@ -1,337 +0,0 @@
|
||||
[#]: collector: (lujun9972)
|
||||
[#]: translator: (lxbwolf)
|
||||
[#]: reviewer: (wxy)
|
||||
[#]: publisher: ( )
|
||||
[#]: url: ( )
|
||||
[#]: subject: (How to program with Bash: Loops)
|
||||
[#]: via: (https://opensource.com/article/19/10/programming-bash-loops)
|
||||
[#]: author: (David Both https://opensource.com/users/dboth)
|
||||
|
||||
Bash 编程教程之循环
|
||||
======
|
||||
本文是 bash 编程系列（3 部分）的最后一篇，来学习使用循环执行迭代的操作。
|
||||
![arrows cycle symbol for failing faster][1]
|
||||
|
||||
Bash 是一种强大的用于命令行和 shell 脚本里的编程语言。本系列的三部分都是基于我的 [Linux 自学课程三卷][2] 写的，探索怎么用 CLI（command-line interface）进行 bash 编程。本系列的 [第一篇文章][3] 讨论了 bash 编程的一些简单命令行操作，如使用变量和控制操作符。[第二篇文章][4] 探讨了文件、字符串、数字等类型和各种各样在执行流中提供控制逻辑的的逻辑运算符，还有 bash 中不同种类的扩展。本文是第三篇（也是最后一篇），意在考察在各种迭代的操作中使用循环以及怎么合理控制循环。
|
||||
|
||||
### 循环
|
||||
|
||||
我使用过的所有编程语言都有很多种循环结构来用来执行重复的操作。我经常使用 for 循环，然而我发现 while 和 until 循环也很有用处。
|
||||
|
||||
#### for 循环
|
||||
|
||||
我的理解是，**for** 命令在 bash 中的实现比大部分语言灵活，因为它可以处理非数字的值；与之形成对比的是，诸如标准 C 语言的 **for** 循环只能处理数字类型的值。
|
||||
|
||||
Bash 版的 **for** 命令基本的结构很简单：
|
||||
|
||||
|
||||
```
|
||||
`for Var in list1 ; do list2 ; done`
|
||||
```
|
||||
|
||||
解释一下：“对于 list1 中的每一个值，把 **$Var** 设置为那个值，使用该值执行 list2 中的程序语句；list1 中的值都执行完后，整个循环结束，退出循环。” list1 中的值可以是一个简单的显式字符串值，也可以是一个命令执行后的结果（译注：**\` \`** 包含的命令执行的结果，本系列第二篇文章中有描述）。我经常使用这种结构。
|
||||
|
||||
确认 **~/testdir** 仍然是当前的工作目录（PWD）。删除目录下所有东西，来看下这个显式写出值列表的 **for** 循环的简单的示例。这个列表中的值是字母值 — 但是不要忘了，在 bash 中所有的变量都是 string 或者可以被当成 string 来处理。
|
||||
|
||||
|
||||
```
|
||||
[student@studentvm1 testdir]$ rm *
|
||||
[student@studentvm1 testdir]$ for I in a b c d 1 2 3 4 ; do echo $I ; done
|
||||
a
|
||||
b
|
||||
c
|
||||
d
|
||||
1
|
||||
2
|
||||
3
|
||||
4
|
||||
```
|
||||
|
||||
给变量赋予更有意义的名字，变成前面版本的进阶版：
|
||||
|
||||
|
||||
```
|
||||
[student@studentvm1 testdir]$ for Dept in "Human Resources" Sales Finance "Information Technology" Engineering Administration Research ; do echo "Department $Dept" ; done
|
||||
Department Human Resources
|
||||
Department Sales
|
||||
Department Finance
|
||||
Department Information Technology
|
||||
Department Engineering
|
||||
Department Administration
|
||||
Department Research
|
||||
```
|
||||
|
||||
创建几个目录（创建时显示一些处理信息）：
|
||||
|
||||
|
||||
```
|
||||
[student@studentvm1 testdir]$ for Dept in "Human Resources" Sales Finance "Information Technology" Engineering Administration Research ; do echo "Working on Department $Dept" ; mkdir "$Dept" ; done
|
||||
Working on Department Human Resources
|
||||
Working on Department Sales
|
||||
Working on Department Finance
|
||||
Working on Department Information Technology
|
||||
Working on Department Engineering
|
||||
Working on Department Administration
|
||||
Working on Department Research
|
||||
[student@studentvm1 testdir]$ ll
|
||||
total 28
|
||||
drwxrwxr-x 2 student student 4096 Apr 8 15:45 Administration
|
||||
drwxrwxr-x 2 student student 4096 Apr 8 15:45 Engineering
|
||||
drwxrwxr-x 2 student student 4096 Apr 8 15:45 Finance
|
||||
drwxrwxr-x 2 student student 4096 Apr 8 15:45 'Human Resources'
|
||||
drwxrwxr-x 2 student student 4096 Apr 8 15:45 'Information Technology'
|
||||
drwxrwxr-x 2 student student 4096 Apr 8 15:45 Research
|
||||
drwxrwxr-x 2 student student 4096 Apr 8 15:45 Sales
|
||||
```
|
||||
|
||||
在 **mkdir** 语句中 **$Dept** 变量必须用引号包裹起来；否则名字中间有空格（如 `Information Technology`）会被当做两个独立的目录处理。我一直信奉的一条实践规则：所有的文件和目录都应该为一个单词（中间没有空格）。虽然大部分现代的操作系统可以处理名字中间有空格的情况，但是系统管理员需要花费额外的精力去确保脚本和 CLI 程序能正确处理这些特例。（尽管你因为不知道将要处理什么样的文件而烦恼，但是脚本和 CLI 应该已经把这些特例考虑在内了。）
|
||||
|
||||
再次删除 **~/testdir** 下的所有东西 — 再运行一次下面的命令：
|
||||
|
||||
|
||||
```
|
||||
[student@studentvm1 testdir]$ rm -rf * ; ll
|
||||
total 0
|
||||
[student@studentvm1 testdir]$ for Dept in Human-Resources Sales Finance Information-Technology Engineering Administration Research ; do echo "Working on Department $Dept" ; mkdir "$Dept" ; done
|
||||
Working on Department Human-Resources
|
||||
Working on Department Sales
|
||||
Working on Department Finance
|
||||
Working on Department Information-Technology
|
||||
Working on Department Engineering
|
||||
Working on Department Administration
|
||||
Working on Department Research
|
||||
[student@studentvm1 testdir]$ ll
|
||||
total 28
|
||||
drwxrwxr-x 2 student student 4096 Apr 8 15:52 Administration
|
||||
drwxrwxr-x 2 student student 4096 Apr 8 15:52 Engineering
|
||||
drwxrwxr-x 2 student student 4096 Apr 8 15:52 Finance
|
||||
drwxrwxr-x 2 student student 4096 Apr 8 15:52 Human-Resources
|
||||
drwxrwxr-x 2 student student 4096 Apr 8 15:52 Information-Technology
|
||||
drwxrwxr-x 2 student student 4096 Apr 8 15:52 Research
|
||||
drwxrwxr-x 2 student student 4096 Apr 8 15:52 Sales
|
||||
```
|
||||
|
||||
假设现在有个需求，需要列出一台 Linux 机器上所有的 RPM 包并对每个包附上简短的描述。我为North Carolina 州工作的时候，曾经遇到过这种需求。由于当时州代理处不允许使用开源的工具，而且我对 Linux 不够熟悉，对技术一窍不通的老板（PHB）需要我列出我计算机上安装的所有软件，这样他们就可以“查看“计算机上有没有安装异常的软件了。
|
||||
|
||||
你怎么实现它？有一种方法是，已知 **rpm –qa** 命令提供了 RPM 包的完整描述，包括 PHB 想要的东西：软件名称和概要描述。一步步执行出最后的结果。首先，列出所有的 RPM 包：
|
||||
|
||||
|
||||
```
|
||||
[student@studentvm1 testdir]$ rpm -qa
|
||||
perl-HTTP-Message-6.18-3.fc29.noarch
|
||||
perl-IO-1.39-427.fc29.x86_64
|
||||
perl-Math-Complex-1.59-429.fc29.noarch
|
||||
lua-5.3.5-2.fc29.x86_64
|
||||
java-11-openjdk-headless-11.0.ea.28-2.fc29.x86_64
|
||||
util-linux-2.32.1-1.fc29.x86_64
|
||||
libreport-fedora-2.9.7-1.fc29.x86_64
|
||||
rpcbind-1.2.5-0.fc29.x86_64
|
||||
libsss_sudo-2.0.0-5.fc29.x86_64
|
||||
libfontenc-1.1.3-9.fc29.x86_64
|
||||
<snip>
|
||||
```
|
||||
|
||||
用 **sort** 和 **uniq** 命令对列表进行排序和打印去重后的结果（有些已安装的 RPM 包具有相同的名字：）
|
||||
|
||||
|
||||
```
|
||||
[student@studentvm1 testdir]$ rpm -qa | sort | uniq
|
||||
a2ps-4.14-39.fc29.x86_64
|
||||
aajohan-comfortaa-fonts-3.001-3.fc29.noarch
|
||||
abattis-cantarell-fonts-0.111-1.fc29.noarch
|
||||
abiword-3.0.2-13.fc29.x86_64
|
||||
abrt-2.11.0-1.fc29.x86_64
|
||||
abrt-addon-ccpp-2.11.0-1.fc29.x86_64
|
||||
abrt-addon-coredump-helper-2.11.0-1.fc29.x86_64
|
||||
abrt-addon-kerneloops-2.11.0-1.fc29.x86_64
|
||||
abrt-addon-pstoreoops-2.11.0-1.fc29.x86_64
|
||||
abrt-addon-vmcore-2.11.0-1.fc29.x86_64
|
||||
<snip>
|
||||
```
|
||||
|
||||
以上命令得到了想要的 RPM 列表，因此你可以把这个列表作为一个循环的输入信息，循环最终会打印每个 RPM 包的详细信息：
|
||||
|
||||
|
||||
```
|
||||
[student@studentvm1 testdir]$ for RPM in `rpm -qa | sort | uniq` ; do rpm -qi $RPM ; done
|
||||
```
|
||||
|
||||
这段代码产出了多余的信息。当循环结束后， 下一步就是提取出 PHB 需要的信息。因此，添加一个 **egrep** 命令用来搜索匹配 **^Name** 或 **^Summary** 的行。脱字符（^）表示行首，整个命令表示显示所有以 Name 或 Summary 开头的行。
|
||||
|
||||
|
||||
```
|
||||
[student@studentvm1 testdir]$ for RPM in `rpm -qa | sort | uniq` ; do rpm -qi $RPM ; done | egrep -i "^Name|^Summary"
|
||||
Name : a2ps
|
||||
Summary : Converts text and other types of files to PostScript
|
||||
Name : aajohan-comfortaa-fonts
|
||||
Summary : Modern style true type font
|
||||
Name : abattis-cantarell-fonts
|
||||
Summary : Humanist sans serif font
|
||||
Name : abiword
|
||||
Summary : Word processing program
|
||||
Name : abrt
|
||||
Summary : Automatic bug detection and reporting tool
|
||||
<snip>
|
||||
```
|
||||
|
||||
在上面的命令中你可以试试用 **grep** 代替 **egrep** ，你会发现用 **grep** 不能得到正确的结果。你可以通过管道把命令结果用 **less** 过滤下。最终命令像这样：
|
||||
|
||||
|
||||
```
|
||||
[student@studentvm1 testdir]$ for RPM in `rpm -qa | sort | uniq` ; do rpm -qi $RPM ; done | egrep -i "^Name|^Summary" > RPM-summary.txt
|
||||
```
|
||||
|
||||
这个命令行程序在同一行中用到了管道、重定向和 **for** 循环。它把你 CLI 程序的结果重定向到了一个文件，这个文件可以在邮件中使用或在其他地方作为输入使用。这个一次一步构建程序的过程让你能看到每步的结果，以此来确保整个程序以你期望的流程进行且输出你想要的结果。
|
||||
|
||||
PHB 最终收到了超过 1900 个独立 RPM 包的清单，我严重怀疑根本就没人去读它。我给了他们想要的东西，没有从他们嘴里听到过任何关于 RPM 包的信息。
|
||||
|
||||
### 其他循环
|
||||
|
||||
Bash 中还有两种其他类型的循环结构：**while** 和 **until** 结构，两者在语法和功能上都类似。这些循环结构的基础语法很简单：
|
||||
|
||||
|
||||
```
|
||||
while [ expression ] ; do list ; done
|
||||
```
|
||||
|
||||
逻辑解释：表达式（expression）结果为 true 时，执行程序语句 `list`。表达式结果为 false 时，退出循环。
|
||||
|
||||
|
||||
```
|
||||
until [ expression ] ; do list ; done
|
||||
```
|
||||
|
||||
逻辑解释：直到表达式的结果为 true，执行程序语句 `list`。当表达式结果为 true 时，退出循环。
|
||||
|
||||
#### While 循环
|
||||
|
||||
**while** 循环用于当逻辑表达式结果为 true 时执行一系列程序语句。假设你的 PWD 仍是 **~/testdir** 。最简单的 **while** 循环会一直运行下去。下面格式的条件语句永远以 `true` 作为返回。你也可以用简单的 `1` 代替 `true` — 结果一样 — 但是这解释了 true 表达式的用法。
|
||||
|
||||
|
||||
```
|
||||
[student@studentvm1 testdir]$ X=0 ; while [ true ] ; do echo $X ; X=$((X+1)) ; done | head
|
||||
0
|
||||
1
|
||||
2
|
||||
3
|
||||
4
|
||||
5
|
||||
6
|
||||
7
|
||||
8
|
||||
9
|
||||
[student@studentvm1 testdir]$
|
||||
```
|
||||
|
||||
既然你已经学了 CLI 的各部分知识，那就让它变得更有用处。首先，为了防止变量 **$X** 在前面的程序或 CLI 命令执行后有遗留的值，设置 **$X** 的值为 0。然后，因为逻辑表达式 **[ true ]** 的结果永远是 1，即 true，在 **do** 和 **done** 中间的程序指令列表会一直执行 — 或者直到你按下 **Ctrl+C** 抑或发送一个 `signal 2` 给程序。那些程序指令是算法扩展，用来打印变量 **$X** 当前的值并加 1.
|
||||
|
||||
[系统管理员的 Linux 哲学][5] 的信条之一是追求优雅，实现优雅的一种方式就是简化。你可以用操作符 **++** 来简化这个程序。在第一个例子中，变量当前的值被打印出来，然后变量的值增加了。可以在变量后加一个 **++** 来表示这个逻辑：
|
||||
|
||||
|
||||
```
|
||||
[student@studentvm1 ~]$ X=0 ; while [ true ] ; do echo $((X++)) ; done | head
|
||||
0
|
||||
1
|
||||
2
|
||||
3
|
||||
4
|
||||
5
|
||||
6
|
||||
7
|
||||
8
|
||||
9
|
||||
```
|
||||
|
||||
现在删掉程序最后的 **| head** 再运行一次。在这个版本中，变量在值被打印之前就自增了。这是通过在变量之前添加 **++** 操作符实现的。你能看出区别吗？
|
||||
|
||||
|
||||
```
|
||||
[student@studentvm1 ~]$ X=0 ; while [ true ] ; do echo $((++X)) ; done | head
|
||||
1
|
||||
2
|
||||
3
|
||||
4
|
||||
5
|
||||
6
|
||||
7
|
||||
8
|
||||
9
|
||||
```
|
||||
|
||||
你已经把打印变量的值和自增简化到了一条语句。类似 **++** 操作符， 也有 **--** 操作符。你需要一个在循环到某个特定数字时终止循环的方法。把 true 表达式换成一个数字比较表达式来实现它。写一个循环到 5 终止的程序。在下面的示例代码中，你可以看到 **-le** 是 ”小于或等于“ 的数字逻辑操作符。整个语句的意思：只要 **$X** 的值小于或等于 5，循环就一直运行。当 **$X** 增加到 6时，循环终止。
|
||||
|
||||
|
||||
```
|
||||
[student@studentvm1 ~]$ X=0 ; while [ $X -le 5 ] ; do echo $((X++)) ; done
|
||||
0
|
||||
1
|
||||
2
|
||||
3
|
||||
4
|
||||
5
|
||||
[student@studentvm1 ~]$
|
||||
```
|
||||
|
||||
#### Until 循环
|
||||
|
||||
|
||||
|
||||
*until** 命令非常像 **while** 命令。不同之处是，它直到逻辑表达式的值是 `true` 之前，会一直循环。看一下这种结构最简单的格式：
|
||||
|
||||
|
||||
```
|
||||
[student@studentvm1 ~]$ X=0 ; until false ; do echo $((X++)) ; done | head
|
||||
0
|
||||
1
|
||||
2
|
||||
3
|
||||
4
|
||||
5
|
||||
6
|
||||
7
|
||||
8
|
||||
9
|
||||
[student@studentvm1 ~]$
|
||||
```
|
||||
|
||||
它用一个逻辑比较表达式来数到一个特定的值：
|
||||
|
||||
|
||||
```
|
||||
[student@studentvm1 ~]$ X=0 ; until [ $X -eq 5 ] ; do echo $((X++)) ; done
|
||||
0
|
||||
1
|
||||
2
|
||||
3
|
||||
4
|
||||
[student@studentvm1 ~]$ X=0 ; until [ $X -eq 5 ] ; do echo $((++X)) ; done
|
||||
1
|
||||
2
|
||||
3
|
||||
4
|
||||
5
|
||||
[student@studentvm1 ~]$
|
||||
```
|
||||
|
||||
### 总结：
|
||||
|
||||
本系列探讨了构建 bash 命令行程序和 shell 脚本的很多强大的工具。但是这仅仅是你能用 Bash 做的很多有意思的事中的冰山一角，接下来就看你的了。我发现学习 Bash 编程最好的方法就是实践。找一个需要多个 Bash 命令的简单项目然后写一个 CLI 程序。系统管理员们做了很多工作让任务变成 CLI 编程，因此我确信你很容易能找到自动化的任务。很多年前，尽管我对其他的 Shell 语言和 Perl 很熟悉，但还是决定用 Bash 做所有系统管理员的自动化任务。我发现 — 有时稍微搜索一下 — 我可以用 Bash 实现我需要的所有事情。
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: https://opensource.com/article/19/10/programming-bash-loops
|
||||
|
||||
作者：[David Both][a]
|
||||
选题：[lujun9972][b]
|
||||
译者：[lxbwolf](https://github.com/lxbwolf)
|
||||
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
|
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[a]: https://opensource.com/users/dboth
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[b]: https://github.com/lujun9972
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[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/fail_progress_cycle_momentum_arrow.png?itok=q-ZFa_Eh (arrows cycle symbol for failing faster)
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[2]: http://www.both.org/?page_id=1183
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[3]: https://opensource.com/article/19/10/programming-bash-part-1
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[4]: https://opensource.com/article/19/10/programming-bash-part-2
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[5]: https://www.apress.com/us/book/9781484237298
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@ -0,0 +1,70 @@
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[#]: collector: (lujun9972)
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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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[#]: subject: (Customize your Linux desktop with KDE Plasma)
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[#]: via: (https://opensource.com/article/19/12/linux-kde-plasma)
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[#]: author: (Seth Kenlon https://opensource.com/users/seth)
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使用 KDE Plasma 定制 Linux 桌面
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======
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本文是 24 天 Linux 桌面特别系列的一部分。如果你认为没有太多机会进行自定义桌面，KDE Plasma 可能适合你。
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![5 pengiuns floating on iceburg][1]
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KDE 社区的 Plasma 桌面是开源桌面中的巅峰之作。KDE 很早就进入了 Linux 桌面市场，但是由于它的 基础 Qt 工具包当时没有完全开放的许可证，因此才有 [GNOME][2] 桌面。在此之后，Qt 开源了，并且 KDE（及其衍生产品，例如 [Trinity桌面][3]）开始蓬勃发展。
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你可能会在发行版的软件仓库中找到 KDE 桌面，或者可以下载并安装将 KDE 作为默认桌面的发行版。在安装之前，请注意，KDE 提供了完整、集成且强大的桌面体验，因此会同时安装几个 KDE 应用。如果你已经在运行其他桌面，那么将发现有几个冗余的应用（两个 PDF 阅读器、多个媒体播放器、两个或多个文件管理器，等等）。如果你只想尝试而不是一直使用 KDE 桌面，那么可以在虚拟机，如[GNOME Boxes][4]中安装基于 KDE 的发行版，也可以尝试使用可引导的操作系统，例如 [Porteus][5]。
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### KDE 桌面之旅
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乍一看，[KDE Plasma][6] 桌面相对无聊，但让人感到舒适。它有行业标准的布局：左下角弹出应用菜单，中间是任务栏，右边是系统托盘。这正是你对标准家用或商用计算机的期望。
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![KDE Plasma desktop][7]
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但是，使 KDE 与众不同的是，你几乎可以更改任何想要的东西。Qt 工具包可以以令人惊讶的方式分割和重新排列，这意味着你实质上可以使用 KDE 的部件作为基础来设计自己的桌面。桌面行为的可用设置也很多。KDE 可以充当标准桌面，平铺窗口管理器以及两者之间的任意形式。你可以通过窗口类、角色、类型、标题或它们的任意组合来创建自己的窗口规则，因此，如果希望特定应用的行为不同于其他行为，那么可以创建全局设置的例外。
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此外，它还有丰富的小部件集合，使你可以自定义与桌面交互的方式。它有一个类似 GNOME 的全屏应用启动器，一个类似 Unity 的 dock 启动器和仅有图标的任务栏，一个传统的任务栏。你可以在屏幕的任何边缘上创建和放置面板。
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![A slightly customized KDE desktop][8]
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实际上，它有太多的自定义项了，因此 KDE 最常见的批评之一是它的_太过可定制化_，所以请记住，自定义项是可选的。你可以在默认配置下使用 Plasma 桌面，并仅在你认为必要时逐步进行更改。Plasma 桌面配置选项最重要的不是它们的数目，而是它们容易发现和直观，它们都在系统设置应用或者右键单击中。
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事实是，在 KDE 上，几乎绝不会只有一种方法可以完成任何给定的任务，并且它的用户将其视为其最大的优势。KDE 中没有隐含的工作流，只有默认的。并且可以更改所有默认设置，直到你需要桌面做的成为你的习惯。
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### 一致性和集成
|
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KDE 社区以一致性和集成为荣，出色的开发人员、社区管理以及 KDE 库使其成为可能。KDE 的开发人员不只是桌面开发人员。它们提供了[惊人的应用集合][9]，每个应用都使用 KDE 库创建，这些库扩展并标准化了常见的 Qt 小部件。使用 KDE 几个月后，无论是打开 [DigiKam][10] 进行照片管理，还是打开 Kmail 来检查电子邮件，还是打开 KTorrent 来获取最新的 ISO 或者使用 Dolphin 管理文件，你的肌肉记忆会在你思考之前直接带你进入对应 UI。
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|
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![KDE on Porteus][11]
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### 尝试 KDE
|
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KDE 适合所有人。使用其默认设置可获得流畅、原始的桌面体验，或对其进行自定义以使其成为自己专属。它是一个稳定、有吸引力且强大的桌面环境，可能有你想要在 Linux 完成要做的事的一切。
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|
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KDE 最初代表 Kool Desktop Environment，但现在被许多人称为 K Desktop。
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--------------------------------------------------------------------------------
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via: https://opensource.com/article/19/12/linux-kde-plasma
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|
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作者：[Seth Kenlon][a]
|
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选题：[lujun9972][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)
|
||||
|
||||
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/rh_003499_01_linux31x_cc.png?itok=Pvim4U-B (5 pengiuns floating on iceburg)
|
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[2]: https://opensource.com/article/19/12/gnome-linux-desktop
|
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[3]: https://opensource.com/article/19/12/linux-trinity-desktop-environment-tde
|
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[4]: https://opensource.com/article/19/5/getting-started-gnome-boxes-virtualization
|
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[5]: https://opensource.com/article/19/6/linux-distros-to-try
|
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[6]: https://kde.org/plasma-desktop
|
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[7]: https://opensource.com/sites/default/files/uploads/advent-kde-presskit.jpg (KDE Plasma desktop)
|
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[8]: https://opensource.com/sites/default/files/uploads/advent-kde-dock.jpg (A slightly customized KDE desktop)
|
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[9]: https://kde.org/applications/
|
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[10]: https://opensource.com/life/16/5/how-use-digikam-photo-management
|
||||
[11]: https://opensource.com/sites/default/files/uploads/advent-kde.jpg (KDE on Porteus)
|
||||
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