关于进程间通信的Linux小程序

利用工作之余为小伙伴写了份作业,关于进程间通信的。题目如下:

“父进程从键盘上接受1000个数据,对其求和sum1,子进程对这1000个数平方和sum2,结果传给父进程,父进程将sum1+sum2后,打印结果。”

要求:用大小为10的共享区传递1000个数据;子进程用消息机制将sum2传给父进程。 

主要利用共享内存实现进程间通信,使用管道实现进程间竞争关系,FreeBSD下测试通过。代码如下:时间有限,有可能有些不足,希望高手给予指点。

  #include <stdio.h>  #include <string.h>  #include <stdlib.h>  #include <sys/shm.h>  #include <signal.h>    const int key = 0x12345678;  static int pfd1[2], pfd2[2];    #define SHM_LEN (10*1024)  #define VAL_NUM 5    int init_shm() {   int shmid = -1;     shmid = shmget((key_t)key, SHM_LEN, 0666 | IPC_CREAT);   if (shmid < 0) {    printf("shmget failed!n");    exit(-1);   }     return shmid;  }    void cancel_shm(int shmid) {   if (shmctl(shmid, IPC_RMID, 0) == -1) {    printf("shmctl failed!n");    exit(-1);   }    printf("cancel_shm successfully!n");  }    void *shm_get(int shmid) {   void *mem = NULL;     mem = shmat(shmid, 0, 0);   if (mem == (void *)-1) {    printf("shmat failed!n");    exit(-1);   }     return mem;  }    int get_val(int *val, int num) {   int i;   for (i = 0; i < num; i++) {    printf("please input a num:");    scanf("%d", val + i);   }  }  void show_val (int *val, int num) {   int i;   for (i = 0; i < num; i++) {    printf("%dt", *(val + i));   }   printf("n");  }    int add_val (int *val, int num) {   int result = 0;   int i;      for (i = 0; i < num; i++) {    result += *(val + i);   }     return result;  }    int square_val (int *val, int num) {   int result = 0;   int i, tmp;     for (i = 0; i < num; i++) {    tmp = *(val + i);    result += (tmp * tmp);   }     return result;  }    void TELL_WAIT (void) {   if (pipe(pfd1) < 0 || pipe(pfd2) < 0) {    printf("pipe error!n");    exit(-1);   }  }    void TELL_PARENT (pid_t pid) {   if (write(pfd2[1], "c", 1) != 1) {    printf("write error!n");    exit(-1);   }  }    void WAIT_PARENT (void) {   char c;     if (read(pfd1[0], &c, 1) != 1) {    printf("read error!n");    exit(-1);   }  }    void TELL_CHILD (pid_t pid) {   if (write(pfd1[1], "p", 1) != 1) {    printf("write error!n");    exit(-1);   }  }    void WAIT_CHILD (void) {   char c;     if (read(pfd2[0], &c, 1) != 1) {    printf("read error!n");    exit(-1);   }  }    int main(int argc, char *argv[]) {   void *mem = NULL;   int shmid = -1;   pid_t pid = -1;   int val[VAL_NUM];   int result = 0;     shmid = init_shm();      TELL_WAIT();   if ((pid = fork()) < 0) {  //error    printf("fork error!n");     exit(-1);   } else if (pid == 0) {   //child    int result = 0;      WAIT_PARENT();      mem = shm_get(shmid);  //get share memery      memcpy(val, mem, sizeof(int) * VAL_NUM);    result = square_val(val, VAL_NUM);       *(int *)((void *)mem + SHM_LEN - 4) = result;      TELL_PARENT(pid);      exit(1);   } else {      //parent    int child_result = 0;      mem = shm_get(shmid);  //get share memery    get_val(val, VAL_NUM);  //get user input    memcpy(mem, val, sizeof(int) * VAL_NUM); //copy user input to share memery      TELL_CHILD(pid);      result = add_val(val, VAL_NUM);      WAIT_CHILD();    child_result = *(int *)((void *)mem + SHM_LEN - 4);    printf("result:%d, child_result:%d, all:%dn", result, child_result, result + child_result);   }     cancel_shm(shmid);     return 0;  }  

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