pkg/plugin.htm

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  <title>plugin</title>
  
    <meta name="twitter:title" content="Package plugin">
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    <meta name="description" content="Package plugin implements loading and symbol resolution of Go plugins.">
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        <h2 id="pkg-overview">package plugin</h2>

        <p><code>import "plugin"</code>

        <p>
Package plugin implements loading and symbol resolution of Go plugins.
</p>
<p>
Currently plugins only work on Linux.
</p>
<p>
A plugin is a Go main package with exported functions and variables that
has been built with:
</p>
<pre>go build -buildmode=plugin
</pre>
<p>
When a plugin is first opened, the init functions of all packages not
already part of the program are called. The main function is not run.
A plugin is only initialized once, and cannot be closed.</p>


        <h3 id="pkg-index" class="section-header">Index <a class="permalink" href="#pkg-index">&para;</a></h3>

        
        <ul class="list-unstyled">
          
          
            <li><a href="#Plugin">type Plugin</a></li>
            <ul>
            <li><a href="#Open">func Open(path string) (*Plugin, error)</a></li>
            <li><a href="#Plugin.Lookup">func (p *Plugin) Lookup(symName string) (Symbol, error)</a></li>
            </ul>
          
            <li><a href="#Symbol">type Symbol</a></li>
            
            
        </ul>

        
          <span id="pkg-examples"></span>
        

<h4 id="pkg-files">
  <a href="https://github.com/golang/go/blob/master/src/plugin/">Package Files</a>
  <a class="permalink" href="#pkg-files">&para;</a>
</h4>

<p><a href="https://github.com/golang/go/blob/master/src/plugin/plugin.go">plugin.go</a> <a href="https://github.com/golang/go/blob/master/src/plugin/plugin_dlopen.go">plugin_dlopen.go</a> </p>

        
          <h3 id="Plugin" data-kind="t">type <a title="View Source" href="https://github.com/golang/go/blob/master/src/plugin/plugin.go#L20">Plugin</a> <a class="permalink" href="#Plugin">&para;</a> <a class="uses" title="List Uses of This Type" href="https://sourcegraph.com/-/godoc/refs?def=Plugin&amp;pkg=plugin&amp;repo=">Uses</a></h3>
          <div class="decl" data-kind="d"><a title="View Source" href="https://github.com/golang/go/blob/master/src/plugin/plugin.go#L20">❖</a><pre>type Plugin struct {
    <span class="com">// contains filtered or unexported fields</span>
}</pre></div><p>
Plugin is a loaded Go plugin.
</p>

          
            <h4 id="Open" data-kind="f">func <a title="View Source" href="https://github.com/golang/go/blob/master/src/plugin/plugin.go#L29">Open</a> <a class="permalink" href="#Open">&para;</a> <a class="uses" title="List Function Callers" href="https://sourcegraph.com/-/godoc/refs?def=Open&amp;pkg=plugin&amp;repo=">Uses</a></h4>
            <div class="funcdecl decl"><a title="View Source" href="https://github.com/golang/go/blob/master/src/plugin/plugin.go#L29">❖</a><pre>func Open(path <a href="/builtin#string">string</a>) (*<a href="#Plugin">Plugin</a>, <a href="/builtin#error">error</a>)</pre></div><p>
Open opens a Go plugin.
If a path has already been opened, then the existing *Plugin is returned.
It is safe for concurrent use by multiple goroutines.
</p>

            
            <h4 id="Plugin.Lookup" data-kind="m">func (*Plugin) <a title="View Source" href="https://github.com/golang/go/blob/master/src/plugin/plugin.go#L37">Lookup</a> <a class="permalink" href="#Plugin.Lookup">&para;</a> <a class="uses" title="List Method Callers" href="https://sourcegraph.com/-/godoc/refs?def=Plugin%2FLookup&amp;pkg=plugin&amp;repo=">Uses</a></h4>
            <div class="funcdecl decl"><a title="View Source" href="https://github.com/golang/go/blob/master/src/plugin/plugin.go#L37">❖</a><pre>func (p *<a href="#Plugin">Plugin</a>) Lookup(symName <a href="/builtin#string">string</a>) (<a href="#Symbol">Symbol</a>, <a href="/builtin#error">error</a>)</pre></div><p>
Lookup searches for a symbol named symName in plugin p.
A symbol is any exported variable or function.
It reports an error if the symbol is not found.
It is safe for concurrent use by multiple goroutines.
</p>

            
          <h3 id="Symbol" data-kind="t">type <a title="View Source" href="https://github.com/golang/go/blob/master/src/plugin/plugin.go#L73">Symbol</a> <a class="permalink" href="#Symbol">&para;</a> <a class="uses" title="List Uses of This Type" href="https://sourcegraph.com/-/godoc/refs?def=Symbol&amp;pkg=plugin&amp;repo=">Uses</a></h3>
          <div class="decl" data-kind="m"><a title="View Source" href="https://github.com/golang/go/blob/master/src/plugin/plugin.go#L73">❖</a><pre>type Symbol interface{}</pre></div><p>
A Symbol is a pointer to a variable or function.
</p>
<p>
For example, a plugin defined as
</p>
<pre>package main

// // No C code needed.
import &#34;C&#34;

import &#34;fmt&#34;

var V int

func F() { fmt.Printf(&#34;Hello, number %d\n&#34;, V) }
</pre>
<p>
may be loaded with the Open function and then the exported package
symbols V and F can be accessed
</p>
<pre>p, err := plugin.Open(&#34;plugin_name.so&#34;)
if err != nil {
	panic(err)
}
v, err := p.Lookup(&#34;V&#34;)
if err != nil {
	panic(err)
}
f, err := p.Lookup(&#34;F&#34;)
if err != nil {
	panic(err)
}
*v.(*int) = 7
f.(func())() // prints &#34;Hello, number 7&#34;
</pre>

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