Linux 进程间通信 -- 匿名mmap映射

Linux 匿名 mmap

匿名映射：

#include <sys/mman.h>
void *mmap(void *addr, size_t length, int prot, int flags,int fd, off_t offset);
int munmap(void *addr, size_t length);

在调用mmap函数时候，在flags参数那里，设置MAP_ANON，并在fd参数那里设置-1.

因为没有实体文件, 匿名映射不能实现无血缘关系的进程间通通信. 下面是一个父子通信,并且使用struct进程内存映射的实例:

#include <fcntl.h>
#include <stdio.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>

typedef struct _person {
  char name[128];
  int age;
} Person;

int main() {

  int length = sizeof(Person);
  Person *person = (Person *)mmap(NULL, length, PROT_READ | PROT_WRITE,
                                  MAP_SHARED | MAP_ANON, -1, 0);
  if (person == MAP_FAILED) {
    perror("mmap");
    return -1;
  }
  pid_t pid = fork();

  if (pid == 0) {
    sprintf(person->name, "brownfeng");
    person->age = 18;
    printf("child:person.name=%s, person.age=%d\n", person->name, person->age);
    sleep(3);
    printf("child:person.name=%s, person.age=%d\n", person->name, person->age);
  } else if (pid > 0) {
    sleep(1);
    printf("parent:person.name=%s, person.age=%d\n", person->name, person->age);
    sprintf(person->name, "brownfeng -- change");
    person->age = 100;
    printf("parent:person.name=%s, person.age=%d\n", person->name, person->age);
    wait(NULL);
  }

  munmap(person, sizeof(person));
  return 0;
}