# 2021-04-06 `WayneLin1992`
###### tags: `linux2021` `2021-04-06`

## 測驗 `1`
### `run`

static void run(char *c, int t)
{
    char *redir_stdin = NULL, *redir_stdout = NULL;
    int pipefds[2] = {0, 0}, outfd = 0;
    char *v[99] = {0};
    char **u = &v[98]; /* end of words */
    for (;;) {
        c--;
        if (is_delim(*c)) /* if NULL (start of string) or pipe: break */
            break;
        if (!is_special(*c)) {
            c++;    /* Copy word of regular chars into previous u */
            XXXXX /* 在此提交你的程式碼 */
        }
        if (is_redir(*c)) { /* If < or > */
            if (*c == '<')
                redir_stdin = *u;
            else
                redir_stdout = *u;
            if ((u - v) != 98)
                u++;
        }
    }
    if ((u - v) == 98) /* empty input */
        return;

    if (!strcmp(*u, "cd")) { /* built-in command: cd */
        fatal(chdir(u[1]), 0);
        return; /* actually, should run() again */
    }

    if (*c) {
        pipe(pipefds);
        outfd = pipefds[1]; /* write end of the pipe */
    }

    pid_t pid = fork();
    if (pid) { /* Parent or error */
        fatal(pid, 1);
        if (outfd) {
            run(c, outfd);     /* parse the rest of the cmdline */
            close(outfd);      /* close output fd */
            close(pipefds[0]); /* close read end of the pipe */
        }
        wait(0);
        return;
    }

    if (outfd) {
        dup2(pipefds[0], 0); /* dup read fd to stdin */
        close(pipefds[0]);   /* close read fd */
        close(outfd);        /* close output */
    }

    if (redir_stdin) {
        close(0); /* replace stdin with redir_stdin */
        fatal(open(redir_stdin, 0), 1);
    }

    if (t) {
        dup2(t, 1); /* replace stdout with t */
        close(t);
    }

    if (redir_stdout) {
        close(1);
        fatal(creat(redir_stdout, 438), 1); /* replace stdout with redir */
    }
    fatal(execvp(*u, u), 1);
}