example_sysvshm_test.go

Documentation: golang.org/x/sys/unix

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    39  	// slice is no longer valid after detaching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