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<h2><a href="./">Go by Example 中文版</a>: 执行进程</h2>

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<p>在前面的例子中，我们了解了<a href="spawning-processes">生成外部进程</a>的知识，

当我们需要在运行的 Go 流程中访问的外部流程时，便可以执行此操作。

但是有时候，我们只想用其它（也许是非 Go）的进程，来完全替代当前的 Go 进程。

这时，我们可以使用经典的 <a href="http://en.wikipedia.org/wiki/Exec_(operating_system)"><code>exec</code></a> 函数的 Go 的实现。</p>

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<a href="https://play.studygolang.com/p/_nmhf7Ap8xD"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />

<pre class="chroma"><span class="kn">package</span> <span class="nx">main</span>

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<pre class="chroma"><span class="kn">import</span> <span class="p">(</span>

<span class="s">&#34;os&#34;</span>

<span class="s">&#34;os/exec&#34;</span>

<span class="s">&#34;syscall&#34;</span>

<span class="p">)</span>

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<pre class="chroma"><span class="kd">func</span> <span class="nf">main</span><span class="p">()</span> <span class="p">{</span>

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<p>在这个例子中，我们将执行 <code>ls</code> 命令。

Go 要求我们提供想要执行的可执行文件的绝对路径，

所以我们将使用 <code>exec.LookPath</code> 找到它（应该是 <code>/bin/ls</code>）。</p>

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<pre class="chroma">

<span class="nx">binary</span><span class="p">,</span> <span class="nx">lookErr</span> <span class="o">:=</span> <span class="nx">exec</span><span class="p">.</span><span class="nf">LookPath</span><span class="p">(</span><span class="s">&#34;ls&#34;</span><span class="p">)</span>

<span class="k">if</span> <span class="nx">lookErr</span> <span class="o">!=</span> <span class="kc">nil</span> <span class="p">{</span>

<span class="nb">panic</span><span class="p">(</span><span class="nx">lookErr</span><span class="p">)</span>

<span class="p">}</span>

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<p><code>Exec</code> 需要的参数是切片的形式的（不是放在一起的一个大字符串）。

我们给 <code>ls</code> 一些基本的参数。注意，第一个参数需要是程序名。</p>

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<span class="nx">args</span> <span class="o">:=</span> <span class="p">[]</span><span class="kt">string</span><span class="p">{</span><span class="s">&#34;ls&#34;</span><span class="p">,</span> <span class="s">&#34;-a&#34;</span><span class="p">,</span> <span class="s">&#34;-l&#34;</span><span class="p">,</span> <span class="s">&#34;-h&#34;</span><span class="p">}</span>

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<p><code>Exec</code> 同样需要使用<a href="environment-variables">环境变量</a>。

这里我们仅提供当前的环境变量。</p>

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<span class="nx">env</span> <span class="o">:=</span> <span class="nx">os</span><span class="p">.</span><span class="nf">Environ</span><span class="p">()</span>

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<p>这里是真正的 <code>syscall.Exec</code> 调用。

如果这个调用成功，那么我们的进程将在这里结束，并被 <code>/bin/ls -a -l -h</code> 进程代替。

如果存在错误，那么我们将会得到一个返回值。</p>

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<span class="nx">execErr</span> <span class="o">:=</span> <span class="nx">syscall</span><span class="p">.</span><span class="nf">Exec</span><span class="p">(</span><span class="nx">binary</span><span class="p">,</span> <span class="nx">args</span><span class="p">,</span> <span class="nx">env</span><span class="p">)</span>

<span class="k">if</span> <span class="nx">execErr</span> <span class="o">!=</span> <span class="kc">nil</span> <span class="p">{</span>

<span class="nb">panic</span><span class="p">(</span><span class="nx">execErr</span><span class="p">)</span>

<span class="p">}</span>

<span class="p">}</span>

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<p>当我们运行程序时，它会替换为 <code>ls</code>。</p>

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<pre class="chroma">

<span class="gp">$</span> go run execing-processes.go

<span class="go">total 16

</span><span class="go">drwxr-xr-x 4 mark 136B Oct 3 16:29 .

</span><span class="go">drwxr-xr-x 91 mark 3.0K Oct 3 12:50 ..

</span><span class="go">-rw-r--r-- 1 mark 1.3K Oct 3 16:28 execing-processes.go</span></pre>

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<p>注意 Go 没有提供 Unix 经典的 <code>fork</code> 函数。

一般来说，这没有问题，因为启动协程、生成进程和执行进程，

已经涵盖了 fork 的大多数使用场景。</p>

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下一个例子: <a href="signals">信号</a>

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<a href="https://twitter.com/mmcgrana">@mmcgrana</a> 和<a href="https://eli.thegreenplace.net">Eli Bendersky</a>编写 | <a href="https://github.com/gobyexample-cn">gobyexample-cn</a> 翻译 | <a href="https://github.com/gobyexample-cn/gobyexample/issues">反馈</a> | <a href="https://github.com/gobyexample-cn/gobyexample">源码</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a> </p>

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