c - 使过程像二叉树一样，让每个 child 做不同的事情

Question

我正在执行以下程序，我在其中创建各种进程，就像它们是二叉树一样，我希望“左边”的 child 做与“右边”的 child 不同的事情，但它输出了我 2 个 child 在右边或左边有 2 个 child ，我不想要那样。

void slice(int dir){
    if (dir == 1) {
        printf("izq ");
        printf("child pid %d   parent pid %d\n",getpid(),getppid());fflush(stdout);
    }
    else if (dir == 2){
        printf("der ");
        printf("child pid %d   parent pid %d\n",getpid(),getppid());fflush(stdout);
    }
}

void vector(int vector[], int length, int niveles){
    for(int i=1;i<=niveles;i++)
    {
    int error = 0;
pid_t child_pid[2] = { -1, -1 };
for (int dir=0; dir<=1; ++dir) {
    child_pid[dir] = fork();
    if (child_pid[dir] == -1) {
        error = 1;
        perror("fork");
    }

    if (child_pid[dir] == 0) { 
       // Here is where you place the code the child should execute.
       slice(dir);
       exit(0);
    }
}

for (int dir=0; dir<=1; ++dir) {
    if (child_pid[dir] == -1)
       continue;

    int status;
    pid_t pid = waitpid(child_pid[dir], &status, 0);
    if (pid == -1) {
        error = 1;
        perror("waitpid");
    }
    else if (WIFSIGNALED(status)) {
        error = 1;
        fprintf(stderr, "Child was killed by signal %d\n", WTERMSIG(status));
    }
    else if (WEXITSTATUS(status) != 0) {
        error = 1;
        fprintf(stderr, "Child exited with error %d\n", WEXITSTATUS(status));
    }
}

if (error)
   exit(1);
   } 
}

我的目标是为“izq”调用一个函数，它做与“der”不同的事情，同时保持整个二叉树的想法。

Answer 1

请记住，父级和子级都从 fork 继续执行，因此您需要如下内容:

int error = 0;
pit_t child_pid[2] = { -1, -1 };
for (int dir=0; dir<=1; ++dir) {
    child_pid[dir] = fork();
    if (child_pid[dir] == -1) {
        error = 1;
        perror("fork");
    }

    if (child_pid[dir] == 0) { 
       // Here is where you place the code the child should execute.
       exit(0);
    }
}

for (int dir=0; dir<=1; ++dir) {
    if (child_pid[dir] == -1)
       continue;

    int status;
    pid_t pid = waitpid(child_pid[dir], &status, 0);
    if (pid == -1) {
        error = 1;
        perror("waitpid");
    }
    else if (WIFSIGNALED(status)) {
        error = 1;
        fprintf(stderr, "Child was killed by signal %d\n", WTERMSIG(wstatus));
    }
    else if (WEXITSTATUS(status) != 0) {
        error = 1;
        fprintf(stderr, "Child exited with error %d\n", WEXITSTATUS(wstatus));
    }
}

if (error)
   exit(1);