Question

解我偶然拼凑了100个

我正在编写一个客户端服务器程序，其中服务器是一个简单的shell

除了/ bin / sleep之外，所有命令都正常工作 - 即rrsh> /bin/sleep 1&

我已经包含了我的整个shell代码 - 其中包括： - 从有效命令列表中检查命令是否有效 - 然后执行它，如果它是

我的shell代码如下所示：

      while((n = Rio_readlineb(&rio, buf, MAXLINE)) != 0){ //loop until connection has been terminated
  if (!strcmp(buf, "quit\n")){
    printf("User %s disconnected.\n", username);
    flag1 = 0; //the user will need to login again
  }
  if (flag1 == 1){ //the user is loged in
    bg = p3parseline(buf, argv_for_shell);
    strtok(buf, "\n");
    printf("User %s sent the command '%s' to be executed.\n", username, buf);
    strcat(argv_for_shell[0], "\n");

    //check if the command is allowed
    flag2 = 0; //set command allowed? flag back to false
    file = Fopen("rrshcommands.txt", "r");
    while (Fgets(command, MAXLINE, file) != NULL){
      if (!strcmp(argv_for_shell[0], command)){
        flag2 = 1;
      }
    }
    Fclose(file);

    strtok(argv_for_shell[0], "\n");

    if (flag2 == 0){ //case where the command is not allowed
      printf("The command '%s' is not allowed.\n", buf);
      strcpy(buf, "Command not allowed\n");
      Rio_writen(connfd, buf, strlen(buf));
    }
    else{
      if ((pid = fork()) == 0) {   /* Child runs user job */
        printf("Fork/Execing the command %s on behalf of the user.\n", argv_for_shell[0]);
        Dup2(connfd, 1);

        if (execve(argv_for_shell[0], argv_for_shell, environ) < 0) {
          printf("%s: Command not found.\n", argv_for_shell[0]);
          exit(0);
        }
      }
      /* Parent waits for foreground job to terminate */
      if (!bg) {
        int status;
        if (waitpid(pid, &status, 0) < 0)
          unix_error("waitfg: waitpid error");
        memset(&buf[0], 0, sizeof(buf)); //flush the buffer
        Rio_writen(connfd, buf, strlen(buf));
      }
      else{
        memset(&buf[0], 0, sizeof(buf)); //flush the buffer
        Rio_writen(connfd, buf, strlen(buf));
      }
      signal(SIGCHLD, reap_background);
    }
  }
  Close(connfd);
}

当我执行/ bin / sleep 1＆amp;它应该移动到最后一个else块并将空字符串写回客户端

从调试它陷入了一个奇怪的地方

93            if ((pid = fork()) == 0) {   /* Child runs user job */
(gdb) p bg
$1 = 1
(gdb) n
104           if (!bg) {
(gdb) Fork/Execing the command /bin/sleep on behalf of the user.
/bin/sleep: invalid time interval ‘’
Try '/bin/sleep --help' for more information.

你可以看到bg == 1，所以我猜它会在execve代码中挂起 - 这就是我收到错误的原因。但为什么gdb会进入下一行呢？

Answer 1

从睡眠 - 帮助：

Usage: sleep NUMBER[SUFFIX]... or: sleep OPTION Pause for NUMBER seconds

也许您缺少NUMBER / OPTION参数？

/ bin / sleep：无效的时间间隔''

1 个答案: