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.

Index type Plugin func Open(path string) (*Plugin, error) func (p *Plugin) Lookup(symName string) (Symbol, error) type Symbol Package Files

plugin.go plugin_dlopen.go

type Plugin ❖ type Plugin struct { // contains filtered or unexported fields } Plugin is a loaded Go plugin.

func Open

❖ func Open(path string) (*Plugin, error) 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

❖ func (p *Plugin) Lookup(symName string) (Symbol, error) 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 ❖ type Symbol interface{} 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(“”) 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”