/*使用文件I/O實現用戶登錄系統，要求初始化註冊賬戶和密碼，再次打開顯示登錄，可以修改密碼*/
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
void change_word();
void sign_in(); //函數的申明
int main(int argc,char **argv)
{
int choice;
FILE *fd;
printf("please choice:(0)sign in :(1)change password:\n");
scanf("%d",&choice); //做出選擇
switch(choice) //通過switch語句做出判斷
{
case 0:
sign_in(); //登錄就直接進入賬戶和密碼的輸入
break;
case 1:
fd = fopen("log.txt","w+"); //選擇更改密碼就直接清空文本，再登錄
sign_in();
break;
}
return 0;
}
void sign_in()
{
int num1 = 0;
int num2 = 0;
char name[13];
char pass_word[13];
char log_name[13];
char log_word[13];
char buff[100];
FILE *fd;
fd = fopen("log.txt","r+"); //以讀寫方式打開文件
if(fd == NULL)
{
perror("fopen()"); // 判斷是否創建成功
}
if( getc(fd) == EOF) //判斷文件中是否有數據，沒有就執行if語句
{
int n,m;
while(getchar()!='\n'); //再每次輸入前需要清空緩衝區，不然第一個fgets會拿走前次數據
printf("Welcome registered username:\n");
fgets(name,13,stdin); //從鍵盤獲取數據
n = fputs(name,fd); //將數據放入文本
printf("Welcome the registered password:\n");
fgets(pass_word,13,stdin);
m = fputs(pass_word,fd);
if(n >= 0 && m >= 0) //判斷數據是否放入成功成功則返回非負整數
{
printf("log success。\n");
}
}
else
{
int n,m;
while(getchar()!='\n');
printf("You have already registered,please enter your name:\n");
fgets(log_name,sizeof(log_name),stdin);
printf("please enter your password:\n");
fgets(log_word,sizeof(log_word),stdin);
memset(buff, 0, sizeof(buff));
rewind(fd); //將文件的偏移量調整到文件開頭。
fgets(buff,sizeof(buff),fd);
n = strcmp(buff,log_name); //使用strcmp函數判斷兩個字符串是否相同
memset(buff, 0, sizeof(buff));
fgets(buff,sizeof(buff),fd);
m = strcmp(buff,log_word);
memset(buff, 0, sizeof(buff));
if(n == 0 && m == 0)
{
printf("log success.\n");
}
else
printf("enter error.\n");
}
fclose(fd);
}