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268 lines
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<title>Go в примерах: Порождающие процессы (Spawning Processes)</title>
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<div class="example" id="spawning-processes">
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<h2><a href="./">Go в примерах</a>: Порождающие процессы (Spawning Processes)</h2>
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<table>
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<tr>
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<td class="docs">
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<p>Иногда наши программы Go должны порождать другие, не
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Go процессы. Например, подсветка синтаксиса на этом
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сайте <a href="https://github.com/mmcgrana/gobyexample/blob/master/tools/generate.go">реализуется</a>
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путем запуска <a href="http://pygments.org/"><code>pygmentize</code></a>
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процесса из программы Go. Давайте рассмотрим несколько
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примеров порождающих процессов из Go.</p>
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<td class="code empty leading">
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</td>
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<td class="docs">
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<td class="code leading">
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<a href="http://play.golang.org/p/2QNUQPuiFlR" target="_blank"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
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<div class="highlight"><pre><span class="kn">package</span> <span class="nx">main</span>
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</pre></div>
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<td class="docs">
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</td>
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<td class="code leading">
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<div class="highlight"><pre><span class="kn">import</span> <span class="p">(</span>
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<span class="s">"fmt"</span>
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<span class="s">"io/ioutil"</span>
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<span class="s">"os/exec"</span>
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<span class="p">)</span>
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</pre></div>
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</td>
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<td class="docs">
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</td>
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<td class="code leading">
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<div class="highlight"><pre><span class="kd">func</span> <span class="nx">main</span><span class="p">()</span> <span class="p">{</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>Мы начнем с простой команды, которая не принимает
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аргументов или ввода и просто печатает что-то на
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стандартный вывод. Хелпер <code>exec.Command</code> создает
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объект для представления этого внешнего процесса.</p>
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</td>
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<div class="highlight"><pre> <span class="nx">dateCmd</span> <span class="o">:=</span> <span class="nx">exec</span><span class="p">.</span><span class="nx">Command</span><span class="p">(</span><span class="s">"date"</span><span class="p">)</span>
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</pre></div>
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<td class="docs">
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<p><code>.Output</code> - это еще один хелпер, который обрабатывает
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общий случай запуска команды, ожидаетее завершения
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и сбора выходных данных. Если ошибок не было, <code>dateOut</code>
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будет содержать байты с информацией о дате.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="nx">dateOut</span><span class="p">,</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">dateCmd</span><span class="p">.</span><span class="nx">Output</span><span class="p">()</span>
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<span class="k">if</span> <span class="nx">err</span> <span class="o">!=</span> <span class="kc">nil</span> <span class="p">{</span>
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<span class="nb">panic</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
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<span class="p">}</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">"> date"</span><span class="p">)</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nb">string</span><span class="p">(</span><span class="nx">dateOut</span><span class="p">))</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>Далее мы рассмотрим несколько более сложный случай,
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когда мы направляем данные во внешний процесс на
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его <code>stdin</code> и собираем результаты из его <code>stdout</code>.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="nx">grepCmd</span> <span class="o">:=</span> <span class="nx">exec</span><span class="p">.</span><span class="nx">Command</span><span class="p">(</span><span class="s">"grep"</span><span class="p">,</span> <span class="s">"hello"</span><span class="p">)</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>Здесь мы явно получаем каналы ввода-вывода,
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запускаем процесс, записываем в него некоторые
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входные данные, читаем полученный результат и,
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наконец, ожидаем завершения процесса.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="nx">grepIn</span><span class="p">,</span> <span class="nx">_</span> <span class="o">:=</span> <span class="nx">grepCmd</span><span class="p">.</span><span class="nx">StdinPipe</span><span class="p">()</span>
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<span class="nx">grepOut</span><span class="p">,</span> <span class="nx">_</span> <span class="o">:=</span> <span class="nx">grepCmd</span><span class="p">.</span><span class="nx">StdoutPipe</span><span class="p">()</span>
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<span class="nx">grepCmd</span><span class="p">.</span><span class="nx">Start</span><span class="p">()</span>
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<span class="nx">grepIn</span><span class="p">.</span><span class="nx">Write</span><span class="p">([]</span><span class="nb">byte</span><span class="p">(</span><span class="s">"hello grep\ngoodbye grep"</span><span class="p">))</span>
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<span class="nx">grepIn</span><span class="p">.</span><span class="nx">Close</span><span class="p">()</span>
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<span class="nx">grepBytes</span><span class="p">,</span> <span class="nx">_</span> <span class="o">:=</span> <span class="nx">ioutil</span><span class="p">.</span><span class="nx">ReadAll</span><span class="p">(</span><span class="nx">grepOut</span><span class="p">)</span>
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<span class="nx">grepCmd</span><span class="p">.</span><span class="nx">Wait</span><span class="p">()</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>Мы опускаем проверки ошибок в приведенном выше
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примере, но вы можете использовать обычный шаблон
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<code>if err != nil</code> для них. Мы также собираем только
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результаты <code>StdoutPipe</code>, но вы можете собирать
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<code>StderrPipe</code> точно таким же образом.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">"> grep hello"</span><span class="p">)</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nb">string</span><span class="p">(</span><span class="nx">grepBytes</span><span class="p">))</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>Обратите внимание, что при порождении команд нам
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нужно предоставить явно разграниченный массив
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команд и аргументов вместо возможности просто
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передать одну строку командной строки.
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Если вы хотите создать полную команду со строкой,
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вы можете использовать опцию <code>-c</code> в <code>bash</code>:</p>
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</td>
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<td class="code">
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<div class="highlight"><pre> <span class="nx">lsCmd</span> <span class="o">:=</span> <span class="nx">exec</span><span class="p">.</span><span class="nx">Command</span><span class="p">(</span><span class="s">"bash"</span><span class="p">,</span> <span class="s">"-c"</span><span class="p">,</span> <span class="s">"ls -a -l -h"</span><span class="p">)</span>
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<span class="nx">lsOut</span><span class="p">,</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">lsCmd</span><span class="p">.</span><span class="nx">Output</span><span class="p">()</span>
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<span class="k">if</span> <span class="nx">err</span> <span class="o">!=</span> <span class="kc">nil</span> <span class="p">{</span>
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<span class="nb">panic</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
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<span class="p">}</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">"> ls -a -l -h"</span><span class="p">)</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nb">string</span><span class="p">(</span><span class="nx">lsOut</span><span class="p">))</span>
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<span class="p">}</span>
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</pre></div>
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</tr>
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</table>
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<table>
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<tr>
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<td class="docs">
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<p>Порожденные программы возвращают вывод, который
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является таким же, как если бы мы запускали их
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непосредственно из командной строки.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre><span class="gp">$</span> go run spawning-processes.go
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<span class="gp">></span> date
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<span class="go">Wed Oct 10 09:53:11 PDT 2012</span>
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</pre></div>
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</td>
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<td class="docs">
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<td class="code leading">
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<div class="highlight"><pre><span class="gp">></span> grep hello
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<span class="go">hello grep</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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</td>
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<td class="code">
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<div class="highlight"><pre><span class="gp">></span> ls -a -l -h
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<span class="go">drwxr-xr-x 4 mark 136B Oct 3 16:29 .</span>
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<span class="go">drwxr-xr-x 91 mark 3.0K Oct 3 12:50 ..</span>
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<span class="go">-rw-r--r-- 1 mark 1.3K Oct 3 16:28 spawning-processes.go</span>
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</pre></div>
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</tr>
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</table>
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<p class="next">
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Следующий пример: <a href="execing-processes">Исполняющие процессы (Exec'ing Processes)</a>.
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</p>
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<p class="footer">
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by <a href="https://markmcgranaghan.com">Mark McGranaghan</a> | <a href="https://github.com/mmcgrana/gobyexample/blob/master/examples/spawning-processes">source</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a>
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</p>
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</div>
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<script>
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var codeLines = [];
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codeLines.push('');codeLines.push('package main\u000A');codeLines.push('import (\u000A \"fmt\"\u000A \"io/ioutil\"\u000A \"os/exec\"\u000A)\u000A');codeLines.push('func main() {\u000A');codeLines.push(' dateCmd := exec.Command(\"date\")\u000A');codeLines.push(' dateOut, err := dateCmd.Output()\u000A if err != nil {\u000A panic(err)\u000A }\u000A fmt.Println(\"\x3E date\")\u000A fmt.Println(string(dateOut))\u000A');codeLines.push(' grepCmd := exec.Command(\"grep\", \"hello\")\u000A');codeLines.push(' grepIn, _ := grepCmd.StdinPipe()\u000A grepOut, _ := grepCmd.StdoutPipe()\u000A grepCmd.Start()\u000A grepIn.Write([]byte(\"hello grep\\ngoodbye grep\"))\u000A grepIn.Close()\u000A grepBytes, _ := ioutil.ReadAll(grepOut)\u000A grepCmd.Wait()\u000A');codeLines.push(' fmt.Println(\"\x3E grep hello\")\u000A fmt.Println(string(grepBytes))\u000A');codeLines.push(' lsCmd := exec.Command(\"bash\", \"-c\", \"ls -a -l -h\")\u000A lsOut, err := lsCmd.Output()\u000A if err != nil {\u000A panic(err)\u000A }\u000A fmt.Println(\"\x3E ls -a -l -h\")\u000A fmt.Println(string(lsOut))\u000A}\u000A');codeLines.push('');codeLines.push('');codeLines.push('');
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<script src="site.js" async></script>
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