# package plugin

`import "plugin"`

Package plugin implements loading and symbol resolution of Go plugins.

Currently plugins only work on Linux.

A plugin is a Go main package with exported functions and variables that has been built with:

    go build -buildmode=plugin

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.

plugin.go plugin_dlopen.go

## type Plugin

Plugin is a loaded Go plugin.

### func Open

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.

### func (*Plugin) Lookup

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.

## type Symbol

A Symbol is a pointer to a variable or function.

For example, a plugin defined as

    package main

    // // No C code needed.
    import "C"

    import "fmt"

    var V int

    func F() { fmt.Printf("Hello, number %d\n", V) }

may be loaded with the Open function and then the exported package symbols V and F can be accessed

    p, err := plugin.Open("plugin_name.so")
    if err != nil {
    	panic(err)
    }
    v, err := p.Lookup("V")
    if err != nil {
    	panic(err)
    }
    f, err := p.Lookup("F")
    if err != nil {
    	panic(err)
    }
    *v.(*int) = 7
    f.(func())() // prints "Hello, number 7"