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; }

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; }

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

此时执行写操作

yu@ubuntu:~/Linux/211/tongxin$ ./write myfile
//在向myfile文件中写数据

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

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

Linux进程共享通信 -- mmap实现

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