我为什么喜欢 Xonsh
有没有想过用 Python 做你的 shell?
Shell 语言对交互式使用很有用。但是在使用它们作为编程语言时这种优化就需要权衡,有时在编写 shell 脚本时会感觉到这点。
如果你的 shell 也能理解一种更可伸缩的语言会怎样?比如说,Python?
进入 Xonsh。
安装 Xonsh 就像创建虚拟环境一样简单,运行 pip install xonsh [ptk,linux]
,然后运行 xonsh
。
首先,你可能奇怪为什么你的 Python shell 有一个奇怪的提示:
<span class="pln">$ </span><span class="lit">1</span><span class="pun">+</span><span class="lit">1</span>
<span class="lit">2</span>
好的,计算器!
<span class="pln">$ </span><span class="kwd">print</span><span class="pun">(</span><span class="str">"hello world"</span><span class="pun">)</span>
<span class="pln">hello world</span>
我们还可以调用其他函数:
<span class="pln">$ </span><span class="kwd">from</span><span class="pln"> antigravity </span><span class="kwd">import</span><span class="pln"> geohash</span>
<span class="pln">$ geohash</span><span class="pun">(</span><span class="lit">37.421542</span><span class="pun">,</span><span class="pun">-</span><span class="lit">122.085589</span><span class="pun">,</span><span class="pln"> b</span><span class="str">'2005-05-26-10458.68'</span><span class="pun">)</span>
<span class="lit">37.857713</span><span class="pun">-</span><span class="lit">122.544543</span>
然而,我们仍然可以像常规 shell 一样使用它:
<span class="pln">$ </span><span class="kwd">echo</span><span class="str">"hello world"</span>
<span class="pln">hello world</span>
我们甚至可以混搭!
<span class="pln">$ </span><span class="kwd">for</span><span class="pln"> i </span><span class="kwd">in</span><span class="pln"> range</span><span class="pun">(</span><span class="lit">3</span><span class="pun">):</span>
<span class="pun">.</span><span class="pln"> </span><span class="kwd">echo</span><span class="str">"hello world"</span>
<span class="pun">.</span>
<span class="pln">hello world</span>
<span class="pln">hello world</span>
<span class="pln">hello world</span>
Xonsh 支持使用 Prompt Toolkit 补全 shell 命令和 Python 表达式。补全有可视化提示,会显示可能的补全并有下拉列表。
它还支持访问环境变量。它使用简单但强大的启发式方法将 Python 类型应用于环境变量。默认值为 “string”,但是,例如,路径变量是自动列表。
<span class="pln">$ </span><span class="str">'/usr/bin'</span><span class="kwd">in</span><span class="pln"> $PATH</span>
<span class="kwd">True</span>
Xonsh 接受 shell 形式或 Python 形式的布尔快捷运算符:
<span class="pln">$ </span><span class="kwd">cat</span><span class="pln"> things</span>
<span class="pln">foo</span>
<span class="pln">$ </span><span class="kwd">grep</span><span class="pun">-</span><span class="pln">q foo things </span><span class="kwd">and</span><span class="kwd">echo</span><span class="str">"found"</span>
<span class="pln">found</span>
<span class="pln">$ </span><span class="kwd">grep</span><span class="pun">-</span><span class="pln">q bar things </span><span class="pun">&&</span><span class="kwd">echo</span><span class="str">"found"</span>
<span class="pln">$ </span><span class="kwd">grep</span><span class="pun">-</span><span class="pln">q foo things </span><span class="kwd">or</span><span class="kwd">echo</span><span class="str">"found"</span>
<span class="pln">$ </span><span class="kwd">grep</span><span class="pun">-</span><span class="pln">q bar things </span><span class="pun">||</span><span class="kwd">echo</span><span class="str">"found"</span>
<span class="pln">found</span>
这意味着 Python 关键字是被解释了。如果我们想要打印著名的《苏斯博士》书的标题,我们需要引用关键词。
<span class="pln">$ </span><span class="kwd">echo</span><span class="pln"> green eggs </span><span class="str">"and"</span><span class="pln"> ham</span>
<span class="pln">green eggs </span><span class="kwd">and</span><span class="pln"> ham</span>
如果我们不这样做,我们会感到惊讶:
<span class="pln">$ </span><span class="kwd">echo</span><span class="pln"> green eggs </span><span class="kwd">and</span><span class="pln"> ham</span>
<span class="pln">green eggs</span>
<span class="pln">xonsh</span><span class="pun">:</span><span class="typ">For</span><span class="pln"> full traceback </span><span class="kwd">set</span><span class="pun">:</span><span class="pln"> $XONSH_SHOW_TRACEBACK </span><span class="pun">=</span><span class="kwd">True</span>
<span class="pln">xonsh</span><span class="pun">:</span><span class="pln"> subprocess mode</span><span class="pun">:</span><span class="pln"> command </span><span class="kwd">not</span><span class="pln"> found</span><span class="pun">:</span><span class="pln"> ham</span>
<span class="typ">Did</span><span class="pln"> you mean one of the following</span><span class="pun">?</span>
<span class="pln"> </span><span class="kwd">as</span><span class="pun">:</span><span class="pln"> </span><span class="typ">Command</span><span class="pun">(</span><span class="str">/usr/</span><span class="pln">bin</span><span class="pun">/</span><span class="kwd">as</span><span class="pun">)</span>
<span class="pln"> ht</span><span class="pun">:</span><span class="pln"> </span><span class="typ">Command</span><span class="pun">(</span><span class="str">/usr/</span><span class="pln">bin</span><span class="pun">/</span><span class="pln">ht</span><span class="pun">)</span>
<span class="pln"> mag</span><span class="pun">:</span><span class="pln"> </span><span class="typ">Command</span><span class="pun">(</span><span class="str">/usr/</span><span class="pln">bin</span><span class="pun">/</span><span class="pln">mag</span><span class="pun">)</span>
<span class="pln"> ar</span><span class="pun">:</span><span class="pln"> </span><span class="typ">Command</span><span class="pun">(</span><span class="str">/usr/</span><span class="pln">bin</span><span class="pun">/</span><span class="pln">ar</span><span class="pun">)</span>
<span class="pln"> </span><span class="kwd">nm</span><span class="pun">:</span><span class="pln"> </span><span class="typ">Command</span><span class="pun">(</span><span class="str">/usr/</span><span class="pln">bin</span><span class="pun">/</span><span class="kwd">nm</span><span class="pun">)</span>
虚拟环境可能会有点棘手。一般的虚拟环境(取决于它们类似 Bash 的语法)无法工作。但是,Xonsh 自带了一个名为 vox
的虚拟环境管理系统。
vox
可以创建、激活和停用 ~/.virtualenvs
中的环境。如果你用过 virtualenvwrapper
,这就是环境变量所在的地方。
请注意,当前激活的环境不会影响 xonsh
。它无法从激活的环境中导入任何内容。
<span class="pln">$ xontrib load vox</span>
<span class="pln">$ vox create </span><span class="kwd">my</span><span class="pun">-</span><span class="pln">environment </span>
<span class="pun">...</span>
<span class="pln">$ vox activate </span><span class="kwd">my</span><span class="pun">-</span><span class="pln">environment </span>
<span class="typ">Activated</span><span class="str">"my-environment"</span><span class="pun">.</span><span class="pln"> </span>
<span class="pln">$ pip install money </span>
<span class="pun">...</span>
<span class="pln">$ python </span>
<span class="pun">...</span>
<span class="pun">>>></span><span class="kwd">import</span><span class="pln"> money </span>
<span class="pun">>>></span><span class="pln"> money</span><span class="pun">.</span><span class="typ">Money</span><span class="pun">(</span><span class="str">'3.14'</span><span class="pun">)</span><span class="pln"> </span>
<span class="pln">$ </span><span class="kwd">import</span><span class="pln"> money</span>
<span class="pln">xonsh</span><span class="pun">:</span><span class="typ">For</span><span class="pln"> full traceback </span><span class="kwd">set</span><span class="pun">:</span><span class="pln"> $XONSH_SHOW_TRACEBACK </span><span class="pun">=</span><span class="kwd">True</span>
<span class="typ">ModuleNotFoundError</span><span class="pun">:</span><span class="typ">No</span><span class="kwd">module</span><span class="pln"> named </span><span class="str">'money'</span>
第一行启用 vox
:它是一个 xontrib
,是 Xonsh 的一个第三方扩展。xontrib
管理器可以列出所有可能的 xontribs
及其当前状态(已安装、已加载或未加载)。
可以编写一个 xontrib
并上传到 PyPi
以使其可用。但是,最好将它添加到 xontrib
索引中,以便 Xonsh 提前知道它。比如,这能让配置向导建议它。
如果你曾经想过,“Python 可以成为我的 shell 吗?”,然后你只要 pip install xonsh
一下就能知道。
via: https://opensource.com/article/18/9/xonsh-bash-alternative
作者:Moshe Zadka 选题:lujun9972 译者:geekpi 校对:wxy