c - 字符串数组与用户字符串比较给出访问错误

Question

我正在尝试构建一个程序，该程序将从文件中获取登录详细信息(用户名和密码)的列表，并允许您选择输入与批准登录并给出结果。在我的 strcmp 中，我收到了 access violation error 0xC0000005。

#include <stdio.h>
#include <conio.h>
#include<stdlib.h>

FILE *fptr;
void main();
void openFile();
void closeFile();
char approvedUsrnames[3][6];
char approvedPassword[3][6];


void main()
{
    char userPassword[6], usrname[6], inputChar, fileString[6];
    int i;
    openFile();

    int numofLogins= 3;


    if (fptr != NULL)
    {
        printf("\nReading file with scanf\n");
        while (!feof(fptr))
        {
            for (i = 0; i < 3; i++) {
                fgets(approvedUsrnames[i], 6, fptr);
                fgets(approvedPassword[i], 6, fptr);
            }

        }
        closeFile();
    }


    printf("Enter User name: ");
    scanf("%s",usrname);
    printf("Enter the password <any 6 characters>: ");

    for (i = 0; i<6; i++)
    {
        inputChar = _getch();
        userPassword[i] = inputChar;
        inputChar = '*';
        printf("%c", inputChar);
    }//obfuscate the input to the user

    /*If you want to know what you have entered as password, to be removed*/
    printf("\nYour password is %s:", userPassword);


    for (i = 1; i < 3; i++) {
        printf("\Username is good %s\n", approvedUsrnames[i]);

        if (strcmp(approvedUsrnames[i], usrname  == 0)){
            printf("\Username is good\n");
            if (strcmp(userPassword, approvedPassword[i]) == 0) {
                printf("\nPassword is good\n");
            }//end nested if
            else {
                printf("\nPassword is not match\n");
            }
        }//end if
    }//end for

    _getch();

}
void openFile()
{
    fptr = fopen("approvedLogins.dat", "r");
    if (fptr == NULL)
    {
        printf("Error opening file ! \n");
    }
    else {
        printf("Login file read successfully ! \n");
    }
}
void closeFile()
{
    fclose(fptr);
}

Answer 1

@安东尼戈登

1. 字符串 usrname 和 userPassword 很可能没有以 '\0'(空终止符)结尾 a) 因为 scanf() 可能会尝试填充比 usrname 可以捕获的更多的字符 b) for 循环只需迭代 5 次，以便将 userPassword[5] 显式设置为“\0”。 (如果期望使用 6 个字符长的用户名和密码，则将数组的长度从 6 更改为 7 并确保数组 [6] 填充为 '\0')(记住 'C' 数组下标为 0 ..(arraysize-1))

2. 另外，一旦用户名和密码匹配，跳出循环。