#include<stdio.h>
int main() {
	FILE *fp;
	char str[102] = { 0 }, strTemp[100];
	if ((fp = fopen("D:\\demo.txt", "at+")) == NULL) {
		printf("Cannot open file, press any key to exit!\n");
		getch();
		exit(1);
	}
	printf("Input a string:");
	gets(strTemp);		//忽略換行符
	strcat(str, "\n");
	strcat(str, strTemp);
	fputs(str, fp);
	fclose(fp);
	return 0;
}