Linux进程共享通信 -- mmap实现

使用mmap内存映射实现一端写，另一端读的进程间通信

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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 0x1000struct 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$ lsread.c  write.cyu@ubuntu:~/Linux/211/tongxin$ gcc -o write write.cyu@ubuntu:~/Linux/211/tongxin$ gcc -o read read.cyu@ubuntu:~/Linux/211/tongxin$ lsread  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$ lsread  read.c  write  write.c  myfileyu@ubuntu:~/Linux/211/tongxin$ ./read myfile6yu-6m7yu-7w^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$ lsread  read.c  write  write.c