Linux进程共享通信 -- mmap实现
https://blog.csdn.net/y396397735/article/details/50651633
使用mmap内存映射实现一端写，另一端读的进程间通信
写端代码write.c
/*write.c*/
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>
/*映射内存大小*/
#define MAPLEN 0x100
/*定义一个学生信息结构体*/
struct STU
{
int id;
char name[20];
char sex;
};
/*出错信息统一处理函数*/
void sys_err(char *str, int exitno)
{
perror(str);
exit(exitno);
}
int main(int argc, char*argv[])
{
struct STU *pm;//STU结构体指针
int fd, i = 0;
if(argc < 2){
printf("args error\n");
exit(1);
}
fd = open(argv[1], O_RDWR | O_CREAT, 0777); //打开一文件
if(fd < 0){
sys_err("open", 1);
}
if(lseek(fd, MAPLEN - 1, SEEK_SET) < 0){//文件偏移至分配的内存地址末端
sys_err("lseek", 3);
}
if(write(fd, "\0", 1) < 0){ //末端赋值为'\0'
sys_err("write", 4);
}
/*将文件映射至进程的地址空间*/
pm = mmap(NULL, MAPLEN, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
if(pm == MAP_FAILED){
sys_err("mmap", 2);
}
/*关闭文件描述符*/
close(fd);
/*对文件进行写入操作*/
while(1){
pm->id = i;
sprintf(pm->name, "yu-%d", i);
if(i % 2 == 0){
pm->sex = 'm';
}else{
pm->sex = 'w';
}
i++;
sleep(1);
}
munmap(pm, MAPLEN);
return 0;
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读端代码read.c
/*read.c*/
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>
#define MANLEN 0x1000
struct STU
{
int id;
char name[20];
char sex;
};
void sys_err(char *str, int exitno)
{
perror(str);
exit(exitno);
}
int main(int argc, char *argv[])
{
struct STU *pm;
int fd, i = 0;
if (argc < 2) {
printf("args error\n");
exit(1);
}
fd = open(argv[1], O_RDWR);
if (fd < 0){
sys_err("open", 1);
}
pm = mmap(NULL, MAPLEN, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
if(pm == MAP_FAILED){
sys_err("mmap", 2);
}
/*关闭文件*/
close(fd);
/*删除文件*/
unlink(argv[1]);
/*在内存中读数据*/
while(1){
printf("%d\n", pm->id);
printf("%s\n", pm->name);
printf("%c\n", pm->sex);
sleep(1);
}
munmap(pm, MAPLEN);
return 0;
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执行过程：
yu@ubuntu:~/Linux/211/tongxin$ ls
read.c write.c
yu@ubuntu:~/Linux/211/tongxin$ gcc -o write write.c
yu@ubuntu:~/Linux/211/tongxin$ gcc -o read read.c
yu@ubuntu:~/Linux/211/tongxin$ ls
read read.c write write.c- 1
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此时执行写操作
yu@ubuntu:~/Linux/211/tongxin$ ./write myfile
//在向myfile文件中写数据- 1
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另开一终端到当前目录，执行如下读操作：
yu@ubuntu:~/Linux/211/tongxin$ ls
read read.c write write.c myfile
yu@ubuntu:~/Linux/211/tongxin$ ./read myfile
6
yu-6
m
7
yu-7
w
^C//读取写入的内容Ctrl+C退出- 1
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退出后，执行ls，可发现myfile文件已删除
yu@ubuntu:~/Linux/211/tongxin$ ls
read read.c write write.c- 1
- 2
