滚动时位置固定在父div内

Question

#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/wait.h>

struct cmd {
    char *stderr;
    char *argv[100];
};

char *filev[3];

#define CLOSEME(_fd) \
    do { \
        if (_fd < 0) \
            break; \
        close(_fd); \
        _fd = -1; \
    } while (0)

int run_in_background;
int cmdcnt;
struct cmd cmdlist[30];

int
pipeline(void)
{
    int pfd[2] = { -1, -1 };
    struct cmd *cmd;
    char *file;
    int oldfd;
    pid_t pid;
    pid_t lastpid = -1;

    // open the common stderr
    int errfd = -1;
    if (filev[2] != NULL)
        errfd = open(filev[2],O_APPEND | O_CREAT);

    // start all commands
    for (int i = 0; i < cmdcnt; i++) {
        int iam_first = (i == 0);
        int iam_last = (i == (cmdcnt - 1));

        cmd = &cmdlist[i];

        // get previous stage pipe descriptor
        oldfd = pfd[0];

        // create the pipe to the next stage
        if (! iam_last) {
            if (pipe(pfd) < 0)
                exit(1);
        }

        pid = fork();
        lastpid = pid;

        int fd;

        if (pid < 0)
            exit(-1);

        char **argv = cmd->argv;

        // parent process
        if (pid > 0) {
            CLOSEME(pfd[1]);
            continue;
        }

        // child process ...

        // open stdin for _first_ command
        fd = -1;
        if (iam_first) {
            file = filev[0];
            if (file != NULL) {
                fd = open(file, O_RDONLY, 0);
            }
        }

        // connect stdin to previous stage pipe
        else {
            fd = oldfd;
            oldfd = -1;
        }

        // connect stdin to correct source
        if (fd >= 0) {
            dup2(fd, STDIN_FILENO);
            close(fd);
        }
        CLOSEME(oldfd);

        // connect to stderr
        file = cmd->stderr;
        if (file != NULL) {
            fd = creat(file, 0644);
            dup2(fd, STDERR_FILENO);
            close(fd);
        }
        else {
            if (errfd >= 0)
                dup2(errfd, STDERR_FILENO);
        }
        CLOSEME(errfd);

        // connect stdout
        // NOTE: does _not_ handle ">> outf" [only does "> outf"]
        fd = -1;
        if (iam_last) {
            file = filev[1];
            if (file != NULL) {
                fd = open(file, O_WRONLY | O_CREAT, 0644);
                dup2(fd, STDOUT_FILENO);
                close(fd);
            }
        }

        // execute the command
        execvp(argv[0], argv);
        exit(9);
    }

    CLOSEME(errfd);

    int status;
    int last_status = 0;

    // parent waits for all pipeline stages to complete
    if (! run_in_background) {
        while (1) {
            pid = wait(&status);
            if (pid <= 0)
                break;
            if (pid == lastpid) {
                last_status = status;
                break;
            }
        }
    }

    return last_status;
}

.nav-tabs1 {
    justify-content: center;
    text-align: center;
    position: fixed;
    display: block;
    right: -70px;
    top: 0;
}

.parentdiv{
  position: relative
}

我需要为另一个X div内的“ X” div固定位置，并且当我滚动“ Y”时需要固定。

我希望我能按我的要求弄清楚！有了这3张图片，即时通讯试图解释我想要什么：

图片1：“ Y” div中有帖子，“ X” div位于“ Y”中

图片2：滚动时会出现“ Y”格的底部，并且会出现“ X”

图3：但是有一个问题，divX的位置固定，但是当我在父div外部滚动时，我不想在父外部（红线之外）

希望您能清楚地理解我的问题，并且任何人都可以帮助我，很长一段时间以来一直在尝试！！