C语言库rename()函数

#include <stdio.h>

int main () {
   int ret;
   char oldname[] = file.txt;
   char newname[] = newfile.txt;

   ret = rename(oldname, newname);

   if(ret == 0) {
      printf(File renamed successfully);
   } else {
      printf(Error: unable to rename the file);
   }

   return(0);
}