#define _CRT_SECURE_NO_WARNINGS

#include <stdio.h>

#define MAX_LINE_LENGTH 100

int main()
{
	FILE* input = fopen("main.c","r");
	if (input == NULL)
	{
		printf("開啟輸入檔案失敗\n");
		getchar();
		return -1;
	}
	FILE* output = fopen("main.c.bak","w");
	if (output == NULL)
	{
		printf("開啟輸出檔案失敗\n");
		fclose(input);
		getchar();
		return -2;
	}
	char str[MAX_LINE_LENGTH] = { 0 };
	while (fgets(str, MAX_LINE_LENGTH, input) != NULL)
	{
		printf("%s",str);
		fputs(str,output);
	}
	fclose(input);
	fclose(output);
	getchar();
	return 0;
}