C管道，fork，dup和exec（）

Question

我正在尝试通过管道传递字符串列表到子进程，它应该通过/bin/cat使用execl() 。 我之前有工作，除了管道没有关闭所以程序一直在等待。 不知道我做了什么，现在根本不工作。 有人可以看到我的代码并告诉我，我在做什么错误，在子进程中cat没有显示str数据吗？

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

    char *str[] = {"The", "quick", "brown", "fox", "jumped", "over", "the", "lazy", "dog"};
    int fds[TOTAL_CHILDREN];
    int writeFds;
    int catPID;
    int status;

    FILE * write_to_child;

    //create pipe
    if (pipe(fds) == -1) {
        perror("creating pipe: failed");
        exit(EXIT_FAILURE);
    }
    pipe(fds);
    //create subprocess for cat child

    switch (catPID) {
        case 0: // successful creation of child
            close(fds[1]); //close write side from parents
            close(0); //close stdin
            dup(fds[0]); //connect pipe from execl cat to stdin

            execl("/bin/cat", "cat", (char *) 0);
            perror("exec failed!");
            exit(20);
            break;

        case -1: //failure
            perror("fork failed: cat process");
            exit(EXIT_FAILURE);

        default: //parent process
            close(fds[0]);

            writeFds = fds[1];
            write_to_child = fdopen(fds[1], "w");

            if (write_to_child == NULL) {
                perror("write to pipe failed");
                exit(EXIT_FAILURE);
            }
            break;


    }

    int i;
    for (i = 0; i < 9; i++){
        fprintf(write_to_child, "%s\n", str[i]);
    }

    fclose(write_to_child);
    close(writeFds);

    wait(&status);

    return (EXIT_SUCCESS);
}

Answer 1

您可能想要添加该行

catPID = fork();

而且我不确定为什么你有两次pipe(fds)