#include <stdlib.h>#include <stdio.h>#include <limits.h>int main(){ const char *file_name = "filename"; char abs_path_buff[PATH_MAX]; //獲取文件路徑, 填充到abs_path_buff //realpath函數返回: null表示獲取失敗; 否則返回指向abs_path_buff的指針 if(realpath(file_name, abs_path_buff)){  printf("%s %s/n", file_name, abs_path_buff); } else{  printf("the file '%s' is not exist/n", file_name);  } return 0;}