text: #include "unistd.h"
  #include "stdio.h"
  #include "stdlib.h"
  
  /*
   * 测试通过时应输出：
   * "  new fd is 3."
   */
  
  void test_dup(){
  	TEST_START(__func__);
  	int fd = dup(STDOUT);
  	assert(fd >=0);
  	printf("  new fd is %d.\n", fd);
  	TEST_END(__func__);
  }
  
  int main(void) {
  	test_dup();
  	return 0;
  }
  