我可以把数组[x][x]写到管道上吗？

Question

im试图在Linux上运行这个程序，这个程序应该将数组中的数字用管道传递给子代，然后每个子代计算对的gcd。但我得到 "Segmentation fault(core dumped) "ERROR。我检查了子程序的进程，就在子程序的 read() 我试着打印字符串只是为了检查，但它不工作。奇怪的是 read not返回-1，这意味着它的工作。char **arr; 还是说它对管道来说太大了，这就是为什么它崩溃了。谢谢你的帮助。

另外，.v2_child1是好的，问题出在 execvp()

#include <stdarg.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MAX_LINE_LENGTH 100
#define FILE_NAME "numbers.txt"

char** readFromTextFile(char *fileName) {

    FILE *f = fopen(fileName, "r");
    if (f == NULL) {
        printf("Error while opening file!");
        return NULL;
    }
    char *line = (char*) malloc(MAX_LINE_LENGTH * sizeof(char));
    char **pairs = (char**) malloc(50 * sizeof(char*));
    int counter = 0;

    while (!feof(f)) {
        char *num1 = (char*) malloc(sizeof(char) * 2);
        char *num2 = (char*) malloc(sizeof(char) * 2);
        fgets(line, MAX_LINE_LENGTH, f);
        sscanf(line, "%s   %s", num1, num2);
        pairs[counter] = num1;
        pairs[counter + 1] = num2;
        counter += 2;
    }
    pairs[counter] = NULL;
    fclose(f);
    return pairs;
}

int numOfPairs(char **arr) {
    int count = 0;
    while (arr[count] != NULL) {
        count += 1;
    }
    if ((count % 2) != 0) {
        printf("odd amount off numbers");
        return -1;
    } else {
        return count / 2;
    }
}

int main(int argc, char *argv[]) {

    //read the pairs of numbers into array
    char **numbers = readFromTextFile(FILE_NAME);
    //returns the num of pairs to check
    int num_pairs = numOfPairs(numbers);
    //initialize the pipes
    int write_pipe[2], read_pipe[2];

    if (pipe(write_pipe) == -1 || pipe(read_pipe) == -1) {
        fprintf(stderr, "Pipe operation failed!");
        exit(0);
    }

    //child --> parent
    int PARENT_READ = read_pipe[0]; // IN
    int CHILD_WRITE = read_pipe[1]; // OUT

    //parent --> child
    int CHILD_READ = write_pipe[0];
    int PARENT_WRITE = write_pipe[1];

    pid_t status = fork(); // create child number 1

    if (status < 0) { // error ocurred
        fprintf(stderr, "Error with fork");
        exit(0);

    } else if (status > 0) { // parent go here 

        char **to_child1 = (char**) malloc(sizeof(char*) * (num_pairs / 2) * 2);
        for (int i = 0; i < num_pairs / 2; ++i) {
            to_child1[2 * i] = numbers[2 * i];
            to_child1[2 * i + 1] = numbers[2 * i + 1];
        }

        if (close(CHILD_READ) == -1)
            perror("problem while close CHILD_READ");
        if (write(PARENT_WRITE, to_child1, sizeof(char*) * (num_pairs / 2) * 2)
                == -1)
            perror("problem while write to PARENT_WRITE");

        if (close(PARENT_WRITE))
            perror("problem while close PARENT_WRITE");

        printf("wrote from parent to pipe\n\n");


    } else { // child process
        char **first_half = (char**) malloc(
                sizeof(char*) * (num_pairs / 2) * 2);
        printf("Hello form son 1\n");
        if (close(PARENT_WRITE) == -1)
            perror("Error while close");
        read(CHILD_READ, first_half, sizeof(char*) * (num_pairs / 2) * 2);

        printf("child got here"); // not printing this*

        if (close(PARENT_READ) == -1) //read is unused
            perror("Error while close");
        if (dup2(CHILD_WRITE, STDOUT_FILENO) == -1) { //redirecting Stdout to pipe.
            perror("dup2 error");
        }

        char *args[num_pairs / 2 + 1];
        args[0] = "./v2_child1";
        for (int i = 1; i < num_pairs / 2 + 1; ++i) {
            args[i] = first_half[i];
        }
        execvp(args[0], args);

    }
    wait(NULL);
    char **gcds = (char**) malloc(sizeof(char*) * (num_pairs / 2));
    close(CHILD_WRITE);
    read(PARENT_READ, gcds, sizeof(int));
    for (int i = 0; i < num_pairs / 2; ++i) {
        printf("The gcd of %d and %d is: %d - calculated from child 1\n",
                atoi(numbers[i * 2]), atoi(numbers[i * 2 + 1]), atoi(gcds[i]));
    }

    /// another child to be created
}

Answer 1

to_child1 是一个指针数组。指针值只有在创建它们的过程中才有意义。将一个指针写入管子中，就会有 不 复制它所指向的数据。所以当子进程读取指针时，并没有它们所指向的字符串。

由于所有的字符串都只有1个字符，所以不需要使用指针数组，只要做一个数组的 char，并将其写入管道。