[英]Username not written when saving username and password to a file
以下 function 用於登錄系統。 它可以 100% 工作,除了變量“用戶名”(用戶輸入)不寫任何內容/空白(數據丟失),而變量“密碼”完美地寫入數據。
void login()
{
while (1)
{
printf("Enter a selection (number 1 or 2), then press enter.\n\n");
printf("1. Login\n2. Register\n\n");
int selection = 0;
scanf("%d", &selection);
if (selection == 1)
{
FILE *fp;
char username[24] = {'\0'};
printf("\nEnter username:\n");
fgets(username, sizeof(username), stdin);
int c = 0;
while ((c = getchar()) != '\n' && c != EOF);
char password[24] = {'\0'};
printf("\nEnter password:\n");
fgets(password, sizeof(password), stdin);
char extension[4] = ".txt";
char fileName[strlen(username) + strlen(extension) + 1];
strcpy(fileName, username);
strcat(fileName, extension);
fp = fopen(fileName, "r");
if (fp != NULL)
{
char fileContents1[24] = {'\0'};
char fileContents2[24] = {'\0'};
for (int i = 0; i <= 1; i++)
{
if (i == 0)
{
fgets(fileContents1, sizeof(fileContents1), fp);
if (i == 1)
{
fgets(fileContents2, sizeof(fileContents2), fp);
}
}
if ((username == fileContents1) && (password == fileContents2))
{
menu();
} else
{
printf("\nInvalid username or password, try again.\n\n");
continue;
}
}
} else
{
printf("\nError, try again.\n\n");
continue;
}
fclose(fp);
} else if (selection == 2)
{
FILE *fp;
char username[24] = {'\0'};
printf("\nChoose a username:\n");
fgets(username, sizeof(username), stdin);
int c = 0;
while ((c = getchar()) != '\n' && c != EOF);
char password[24] = {'\0'};
printf("\nChoose a password:\n");
fgets(password, sizeof(password), stdin);
char extension[4] = ".txt";
char fileName[strlen(username) + strlen(extension) + 1];
strcpy(fileName, username);
strcat(fileName, extension);
fp = fopen(fileName, "w");
if (fp != NULL)
{
fputs(username, fp);
fputs(password, fp);
printf("\nLogin created successfully.\n\n");
} else
{
printf("\nError, try again.\n\n");
continue;
}
fclose(fp);
} else
{
printf("\nInvalid selection, try again.\n\n");
continue;
}
}
}
至少有這些問題:
剩下的'\n'
scanf("%d", &selection);
在數字之后不消耗任何東西,比如尾隨'\n'
。
fgets()
讀取'\n'
- 很短的一行。
scanf("%d", &selection);
...
fgets(username, sizeof(username), stdin);
最好不要將scanf()
與fgets(...,..., stdin)
混合使用。
最好只使用fgets()
。
記住fgets()
讀取並保存最終'\n'
您可能希望在fgets()
之后刪除潛在'\n'
。
username[strcspn(username, "\n")] = '\0';
指針比較
username == fileContents1
比較兩個字符串的地址。 要比較字符串的內容,請使用strcmp()
。
可疑代碼
int c = 0; while ((c = getchar());= '\n' && c != EOF);
只有在fgets()
未能讀取整行時, fgets()
才有意義。 如果fgets()
這樣做了,那么這個while()
會讀取並拋出下一行。
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