1// Copyright 2021 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5//go:build (darwin && !ios) || (linux && !android)
6// +build darwin,!ios linux,!android
7
8package unix_test
9
10import (
11	"log"
12
13	"golang.org/x/sys/unix"
14)
15
16func ExampleSysvShmGet() {
17	// create shared memory region of 1024 bytes
18	id, err := unix.SysvShmGet(unix.IPC_PRIVATE, 1024, unix.IPC_CREAT|unix.IPC_EXCL|0o600)
19	if err != nil {
20		log.Fatal("sysv shm create failed:", err)
21	}
22
23	// warning: sysv shared memory segments persist even after after a process
24	// is destroyed, so it's very important to explicitly delete it when you
25	// don't need it anymore.
26	defer func() {
27		_, err := unix.SysvShmCtl(id, unix.IPC_RMID, nil)
28		if err != nil {
29			log.Fatal(err)
30		}
31	}()
32
33	// to use a shared memory region you must attach to it
34	b, err := unix.SysvShmAttach(id, 0, 0)
35	if err != nil {
36		log.Fatal("sysv attach failed:", err)
37	}
38
39	// you should detach from the segment when finished with it. The byte
40	// slice is no longer valid after detaching
41	defer func() {
42		if err = unix.SysvShmDetach(b); err != nil {
43			log.Fatal("sysv detach failed:", err)
44		}
45	}()
46
47	// Changes to the contents of the byte slice are reflected in other
48	// mappings of the shared memory identifer in this and other processes
49	b[42] = 'h'
50	b[43] = 'i'
51}
52