/* A pointer to an open file must be passed */

 long nol(FILE *f)
 {      long current_position = ftell(f);
	fseek(f,0L,SEEK_SET);
	for(int nol = 0; !feof(f) ; )
	{	if(fgetc(f)=='\n')
		{ nol ++ ; }
	}
	fseek(f,current_position,SEEK_SET);
	return nol;
 }