Subcommands example
This commit is contained in:
Eli Bendersky
parent
f2f5af3690
commit
738fc184ef
@ -59,6 +59,7 @@ Writing Files
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Line Filters
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Line Filters
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Command-Line Arguments
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Command-Line Arguments
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Command-Line Flags
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Command-Line Flags
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Command-Line Subcommands
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Environment Variables
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Environment Variables
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HTTP Clients
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HTTP Clients
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Spawning Processes
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Spawning Processes
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@ -0,0 +1,57 @@
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// Some command-line tools, like the `go` tool or `git`
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// have many *subcommands*, each with its own set of
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// flags. For example, `go build` and `go get` are two
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// different subcommands of the `go` tool.
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// The `flag` package lets us easily define simple
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// subcommands that have their own flags.
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package main
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import (
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"flag"
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"fmt"
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"os"
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)
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func main() {
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// We declare a subcommand using the `NewFlagSet`
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// function, and proceed to define new flags specific
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// for this subcommand.
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fooCmd := flag.NewFlagSet("foo", flag.ExitOnError)
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fooEnable := fooCmd.Bool("enable", false, "enable")
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fooName := fooCmd.String("name", "", "name")
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// For a different subcommand we can define different
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// supported flags.
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barCmd := flag.NewFlagSet("bar", flag.ExitOnError)
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barLevel := barCmd.Int("level", 0, "level")
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// The subcommand is expected as the first argument
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// to the program.
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if len(os.Args) < 2 {
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fmt.Println("expected 'foo' or 'bar' subcommands")
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os.Exit(1)
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}
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// Check which subcommand is invoked.
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switch os.Args[1] {
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case "foo":
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// For every subcommand, we parse its own flags and
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// have access to trailing positional arguments.
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fooCmd.Parse(os.Args[2:])
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fmt.Println("subcommand 'foo'")
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fmt.Println(" enable:", *fooEnable)
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fmt.Println(" name:", *fooName)
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fmt.Println(" tail:", fooCmd.Args())
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case "bar":
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barCmd.Parse(os.Args[2:])
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fmt.Println("subcommand 'bar'")
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fmt.Println(" level:", *barLevel)
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fmt.Println(" tail:", barCmd.Args())
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default:
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fmt.Println("expected 'foo' or 'bar' subcommands")
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os.Exit(1)
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}
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}
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@ -0,0 +1,2 @@
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673d7811734cfd8f8f5bcb411e12def1e158cf0b
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V7xR3wMkquz
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@ -0,0 +1,21 @@
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$ go build command-line-subcommands.go
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# First invoke the foo subcommand
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$ ./command-line-subcommands foo -enable -name=joe a1 a2
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subcommand 'foo'
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enable: true
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name: joe
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tail: [a1 a2]
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# Now try bar
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$ ./command-line-subcommands bar -level 8 a1
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subcommand 'bar'
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level: 8
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tail: [a1]
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# But bar won't accept foo's flags
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$ ./command-line-subcommands bar -enable a1
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flag provided but not defined: -enable
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Usage of bar:
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-level int
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level
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@ -297,7 +297,7 @@ way to parameterize programs.</p>
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<p class="next">
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<p class="next">
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Next example: <a href="environment-variables">Environment Variables</a>.
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Next example: <a href="command-line-subcommands">Command-Line Subcommands</a>.
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</p>
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</p>
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<p class="footer">
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<p class="footer">
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239
public/command-line-subcommands
Normal file
239
public/command-line-subcommands
Normal file
@ -0,0 +1,239 @@
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<!DOCTYPE html>
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<html>
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<head>
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<meta charset="utf-8">
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<title>Go by Example: Command-Line Subcommands</title>
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<link rel=stylesheet href="site.css">
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</head>
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<body>
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<div class="example" id="command-line-subcommands">
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<h2><a href="./">Go by Example</a>: Command-Line Subcommands</h2>
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<table>
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<tr>
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<td class="docs">
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<p>Some command-line tools, like the <code>go</code> tool or <code>git</code>
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have many <em>subcommands</em>, each with its own set of
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flags. For example, <code>go build</code> and <code>go get</code> are two
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different subcommands of the <code>go</code> tool.
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The <code>flag</code> package lets us easily define simple
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subcommands that have their own flags.</p>
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</td>
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<td class="code empty leading">
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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 leading">
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<a href="http://play.golang.org/p/V7xR3wMkquz"><img title="Run code" class="run" src="data:image/png;base64,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" /></a>
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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>
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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 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">"flag"</span>
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<span class="s">"fmt"</span>
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<span class="s">"os"</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>We declare a subcommand using the <code>NewFlagSet</code>
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function, and proceed to define new flags specific
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for this subcommand.</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">fooCmd</span> <span class="o">:=</span> <span class="nx">flag</span><span class="p">.</span><span class="nx">NewFlagSet</span><span class="p">(</span><span class="s">"foo"</span><span class="p">,</span> <span class="nx">flag</span><span class="p">.</span><span class="nx">ExitOnError</span><span class="p">)</span>
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<span class="nx">fooEnable</span> <span class="o">:=</span> <span class="nx">fooCmd</span><span class="p">.</span><span class="nx">Bool</span><span class="p">(</span><span class="s">"enable"</span><span class="p">,</span> <span class="kc">false</span><span class="p">,</span> <span class="s">"enable"</span><span class="p">)</span>
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<span class="nx">fooName</span> <span class="o">:=</span> <span class="nx">fooCmd</span><span class="p">.</span><span class="nx">String</span><span class="p">(</span><span class="s">"name"</span><span class="p">,</span> <span class="s">""</span><span class="p">,</span> <span class="s">"name"</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>For a different subcommand we can define different
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supported flags.</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">barCmd</span> <span class="o">:=</span> <span class="nx">flag</span><span class="p">.</span><span class="nx">NewFlagSet</span><span class="p">(</span><span class="s">"bar"</span><span class="p">,</span> <span class="nx">flag</span><span class="p">.</span><span class="nx">ExitOnError</span><span class="p">)</span>
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<span class="nx">barLevel</span> <span class="o">:=</span> <span class="nx">barCmd</span><span class="p">.</span><span class="nx">Int</span><span class="p">(</span><span class="s">"level"</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="s">"level"</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>The subcommand is expected as the first argument
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to the program.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="k">if</span> <span class="nb">len</span><span class="p">(</span><span class="nx">os</span><span class="p">.</span><span class="nx">Args</span><span class="p">)</span> <span class="p"><</span> <span class="mi">2</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="s">"expected 'foo' or 'bar' subcommands"</span><span class="p">)</span>
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<span class="nx">os</span><span class="p">.</span><span class="nx">Exit</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span>
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<span class="p">}</span>
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</pre></div>
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</td>
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<tr>
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<td class="docs">
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<p>Check which subcommand is invoked.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="k">switch</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> <span class="p">{</span>
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<span class="k">case</span> <span class="s">"foo"</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>For every subcommand, we parse its own flags and
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have access to trailing positional arguments.</p>
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</td>
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<td class="code">
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<div class="highlight"><pre> <span class="nx">fooCmd</span><span class="p">.</span><span class="nx">Parse</span><span class="p">(</span><span class="nx">os</span><span class="p">.</span><span class="nx">Args</span><span class="p">[</span><span class="mi">2</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="s">"subcommand 'foo'"</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="s">" enable:"</span><span class="p">,</span> <span class="o">*</span><span class="nx">fooEnable</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="s">" name:"</span><span class="p">,</span> <span class="o">*</span><span class="nx">fooName</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="s">" tail:"</span><span class="p">,</span> <span class="nx">fooCmd</span><span class="p">.</span><span class="nx">Args</span><span class="p">())</span>
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<span class="k">case</span> <span class="s">"bar"</span><span class="p">:</span>
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<span class="nx">barCmd</span><span class="p">.</span><span class="nx">Parse</span><span class="p">(</span><span class="nx">os</span><span class="p">.</span><span class="nx">Args</span><span class="p">[</span><span class="mi">2</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="s">"subcommand 'bar'"</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="s">" level:"</span><span class="p">,</span> <span class="o">*</span><span class="nx">barLevel</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="s">" tail:"</span><span class="p">,</span> <span class="nx">barCmd</span><span class="p">.</span><span class="nx">Args</span><span class="p">())</span>
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<span class="k">default</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="s">"expected 'foo' or 'bar' subcommands"</span><span class="p">)</span>
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<span class="nx">os</span><span class="p">.</span><span class="nx">Exit</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span>
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<span class="p">}</span>
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<span class="p">}</span>
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</pre></div>
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</td>
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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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</td>
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<td class="code leading">
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<div class="highlight"><pre><span class="gp">$</span> go build command-line-subcommands.go
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>First invoke the foo subcommand</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre><span class="gp">$</span> ./command-line-subcommands foo -enable -name<span class="o">=</span>joe a1 a2
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<span class="go">subcommand 'foo'</span>
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<span class="go"> enable: true</span>
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<span class="go"> name: joe</span>
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<span class="go"> tail: [a1 a2]</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>Now try bar</p>
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</td>
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||||||
|
<td class="code leading">
|
||||||
|
|
||||||
|
<div class="highlight"><pre><span class="gp">$</span> ./command-line-subcommands bar -level <span class="m">8</span> a1
|
||||||
|
<span class="go">subcommand 'bar'</span>
|
||||||
|
<span class="go"> level: 8</span>
|
||||||
|
<span class="go"> tail: [a1]</span>
|
||||||
|
</pre></div>
|
||||||
|
|
||||||
|
</td>
|
||||||
|
</tr>
|
||||||
|
|
||||||
|
<tr>
|
||||||
|
<td class="docs">
|
||||||
|
<p>But bar won’t accept foo’s flags</p>
|
||||||
|
|
||||||
|
</td>
|
||||||
|
<td class="code">
|
||||||
|
|
||||||
|
<div class="highlight"><pre><span class="gp">$</span> ./command-line-subcommands bar -enable a1
|
||||||
|
<span class="go">flag provided but not defined: -enable</span>
|
||||||
|
<span class="go">Usage of bar:</span>
|
||||||
|
<span class="go"> -level int</span>
|
||||||
|
<span class="go"> bar level</span>
|
||||||
|
</pre></div>
|
||||||
|
|
||||||
|
</td>
|
||||||
|
</tr>
|
||||||
|
|
||||||
|
</table>
|
||||||
|
|
||||||
|
|
||||||
|
<p class="next">
|
||||||
|
Next example: <a href="environment-variables">Environment Variables</a>.
|
||||||
|
</p>
|
||||||
|
|
||||||
|
<p class="footer">
|
||||||
|
by <a href="https://markmcgranaghan.com">Mark McGranaghan</a> | <a href="https://github.com/mmcgrana/gobyexample/blob/master/examples/command-line-subcommands">source</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a>
|
||||||
|
</p>
|
||||||
|
</div>
|
||||||
|
</body>
|
||||||
|
</html>
|
||||||
@ -145,6 +145,8 @@
|
|||||||
|
|
||||||
<li><a href="command-line-flags">Command-Line Flags</a></li>
|
<li><a href="command-line-flags">Command-Line Flags</a></li>
|
||||||
|
|
||||||
|
<li><a href="command-line-subcommands">Command-Line Subcommands</a></li>
|
||||||
|
|
||||||
<li><a href="environment-variables">Environment Variables</a></li>
|
<li><a href="environment-variables">Environment Variables</a></li>
|
||||||
|
|
||||||
<li><a href="http-clients">HTTP Clients</a></li>
|
<li><a href="http-clients">HTTP Clients</a></li>
|
||||||
|
|||||||
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Reference in New Issue
Block a user