【linux】——一个小程序

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("%d\t", *(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:%d\n", result, child_result, result + child_result);
    }

    cancel_shm(shmid);

    return 0;
}