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command-line-arguments
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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Go by Example: Command-Line Arguments</title>
<link rel=stylesheet href="site.css">
</head>
<script>
onkeydown = (e) => {
if (e.key == "ArrowLeft") {
window.location.href = 'testing-and-benchmarking';
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if (e.key == "ArrowRight") {
window.location.href = 'command-line-flags';
}
}
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<body>
<div class="example" id="command-line-arguments">
<h2><a href="./">Go by Example</a>: Command-Line Arguments</h2>
<table>
<tr>
<td class="docs">
<p><a href="http://en.wikipedia.org/wiki/Command-line_interface#Arguments"><em>Command-line arguments</em></a>
are a common way to parameterize execution of programs.
For example, <code>go run hello.go</code> uses <code>run</code> and
<code>hello.go</code> arguments to the <code>go</code> program.</p>
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<td class="code empty leading">
</td>
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<td class="docs">
</td>
<td class="code leading">
<a href="http://play.golang.org/p/oSxtj7v_v1K"><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>
</pre>
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<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"><span class="kn">import</span> <span class="p">(</span>
<span class="s">"fmt"</span>
<span class="s">"os"</span>
<span class="p">)</span>
</pre>
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<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"><span class="kd">func</span> <span class="nf">main</span><span class="p">()</span> <span class="p">{</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p><code>os.Args</code> provides access to raw command-line
arguments. Note that the first value in this slice
is the path to the program, and <code>os.Args[1:]</code>
holds the arguments to the program.</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">argsWithProg</span> <span class="o">:=</span> <span class="nx">os</span><span class="p">.</span><span class="nx">Args</span>
<span class="nx">argsWithoutProg</span> <span class="o">:=</span> <span class="nx">os</span><span class="p">.</span><span class="nx">Args</span><span class="p">[</span><span class="mi">1</span><span class="p">:]</span>
</pre>
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<tr>
<td class="docs">
<p>You can get individual args with normal indexing.</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">arg</span> <span class="o">:=</span> <span class="nx">os</span><span class="p">.</span><span class="nx">Args</span><span class="p">[</span><span class="mi">3</span><span class="p">]</span>
</pre>
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<td class="docs">
</td>
<td class="code">
<pre class="chroma"> <span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">argsWithProg</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">argsWithoutProg</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">arg</span><span class="p">)</span>
<span class="p">}</span>
</pre>
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</table>
<table>
<tr>
<td class="docs">
<p>To experiment with command-line arguments it’s best to
build a binary with <code>go build</code> first.</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="gp">$</span> go build command-line-arguments.go
<span class="gp">$</span> ./command-line-arguments a b c d
<span class="go">[./command-line-arguments a b c d]
</span><span class="go">[a b c d]
</span><span class="go">c</span></pre>
</td>
</tr>
<tr>
<td class="docs">
<p>Next we’ll look at more advanced command-line processing
with flags.</p>
</td>
<td class="code empty">
</td>
</tr>
</table>
<p class="next">
Next example: <a href="command-line-flags">Command-Line Flags</a>.
</p>
<p class="footer">
by <a href="https://markmcgranaghan.com">Mark McGranaghan</a> and <a href="https://eli.thegreenplace.net">Eli Bendersky</a> | <a href="https://github.com/mmcgrana/gobyexample">source</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a>
</p>
</div>
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