Custom usage of yywrap() in a LEX program

yywrap_usage_example.c

/* Declarations */

%%

/* Rules */

%%

int yywrap()
{
  FILE *newfile_pointer;
  newfile_pointer = fopen("input_file_2.l","r");
  if(yyin != newfile_pointer)
  {
    yyin = newfile_pointer;
    return 0;
  }
  else
  return 1;
}

int main()
{
  yyin = fopen("input_file.l","r");
  yylex();
  return 1;
}