Ç管，叉，DUP，和exec（） [英] C pipe, fork, dup, and exec()

问题描述

我想通过管道传递的字符串列表到子进程，它应该 /斌/猫使用 EXECL（）显示通过。我是有工作的前面除了管道没有关闭使程序一直在等待。不知道我做了什么，现在它不工作。有人可以看到我的code，并告诉我，我做错了 STR 数据没有在子过程中显示由猫？

  INT主（INT ARGC，字符** argv的）{    字符*海峡[] = {的，快速，棕色，狐狸精，跳楼，过，了，懒惰，狗};
    INT FDS [TOTAL_CHILDREN]
    INT writeFds;
    INT catPID;
    INT状态;    FILE * write_to_child;    //创建管
    如果（管（FDS）== -1）{
        PERROR（创建管道：失败）;
        出口（EXIT_FAILURE）;
    }
    管（FDS）;
    //创建猫子子    开关（catPID）{
        案件0：//创建成功的孩子
            关闭（FDS [1]）; //家长密切写入端
            关闭（0）; //关闭标准输入
            DUP（FDS [0]）; //从EXECL猫连接管标准输入            EXECL（/斌/猫，猫，（字符*）0）;
            PERROR（EXEC失败！）;
            出口（20）;
            打破;        案例-1：//失败
            PERROR（叉失败：cat进程）;
            出口（EXIT_FAILURE）;        默认：//父进程
            关闭（FDS [0]）;            writeFds = FDS [1];
            write_to_child = fdopen（FDS [1]，W）;            如果（write_to_child == NULL）{
                PERROR（写管道失败）;
                出口（EXIT_FAILURE）;
            }
            打破;
    }    INT I;
    对于（i = 0; I＆LT; 9;我++）{
        fprintf中（write_to_child％s \\ n，海峡[I]）;
    }    FCLOSE（write_to_child）;
    关闭（writeFds）;    等待（安培;状态）;    回报（EXIT_SUCCESS）;
}
 

解决方案

您可能要添加的行

  catPID = fork（）的;
 

和我不知道为什么你有管（FDS）两次

I'm trying to pass list of strings through pipe to child process where it should display through /bin/cat using execl(). I had it working earlier except that the pipe did not close so the program kept waiting. Don't know what I did and now it is not working at all. Can someone see my code and tell me what am I doing wrong that the str data is not being displayed by cat in child process?

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);
}

解决方案

You probably want to add the line

catPID = fork();

and I'm not sure why you've got pipe(fds) twice

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