c - C编程如何限制用户输入相同的用户名

Question

我目前正在做客户忠诚度系统，需要注册用户名和密码。我需要限制用户输入相同的用户名，但我找不到任何信息。预先感谢您帮助我。

我将所有内容存储在文本文件中。

printf("\t\t\t\t\t   Enter Your Username: ");
scanf("%s", &Username);
printf("\t\t\t\t\t   Enter Your Password: ");
scanf("%s", &Password);
//adding varable named NumofCust
NumOfCust++;
int i = 0;
//variable for boolean logic
int flag = 0;
int ch = 0;
int Points = 0;
for (i = 0; i <= NumOfCust; i++)
{
    if (strcmp(user[i].Username, Username) == 0)
    {
        flag = 1;
        break;
    }
}

if (flag == 0)
{
    strcpy(user[i].Username, Username);
    strcpy(user[i].Password, Password);
};

//opening txt file read, append, and write
FILE *readfile = fopen("CustomerRegistration.txt", "r");
if (readfile)
{
    FILE *CreateFile = fopen("CustomerRegistration.txt", "a");
    fprintf(CreateFile, "%s\n%s\n%d\n", Username, Password, Points);
    fclose(CreateFile);
    printf("\t\t\t\t\tRegistration is Successful!!!\n\t\t\t\t\t");
}

else
{
    FILE *CreateFile = fopen("CustomerRegistration.txt", "w");
    fprintf(CreateFile, "%s\n%s\n%d\n", Username, Password, Points);
    fclose(CreateFile);
    printf("\t\t\t\t\tRegistration is Successful!!!\n\t\t\t\t\t");
}
system("pause");

Answer 1

您可以组织文本文件，因为每一行都是一个用户名，然后当用户注册帐户时解析该用户名的文本文件

bool isOriginalUsername(string name){
ifstream file;
file.open(//the file);
string line;
while(getline(file, line)
{
  for(int i = 0; i > //number of users; i++)
  {
    if(name == line)
    {
    return false;
    }
    getline(file, line)
  }
}
}