C库函数 perror()

#include <stdio.h>



int main () {

   FILE *fp;



   /* first rename if there is any file */

   rename("file.txt", "newfile.txt");



   /* now let's try to open same file */

   fp = fopen("file.txt", "r");

   if( fp == NULL ) {

      perror("Error: ");

      return(-1);

   }



   fclose(fp);

   return(0);

}