c - 根据输出搜索 .txt 文件

Question

我制作了一个密码生成器...然后生成一个 12 个字符的密码，然后将密码保存到 .txt 文件中。我希望能够搜索 .txt 文件，这样就不会创建相同的两个密码。老实说，我不知道如何解决这个问题，并且非常感谢一些帮助。

我的密码生成器正在工作，并且密码保存得很好。

#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#include <string.h>


FILE*fp; 

char *symbols = "#~!$%^&*()+=<>?/@"; // Random Symbol is generated form this list

int main(void) {

    char password[4 + 4 + 2 + 2 + 1]; // 4 Upper, 4 Lower, 2 Num, 2 Symbols
    int i, j=0, len=sizeof(password)-1;
    int menuNum = 0;
    char passwordCheck[15+1];

    fp = fopen("passwords.txt", "a+"); //Opens the text file to save the Passwords

    srand(time(NULL));
    printf("       Main Menu\n");
    printf("********************************\n");
    printf("\nEnter 1 to Generate a New Password: ");
    printf("\n\n");
    printf("Enter 2 to Check Old Passwords: ");
    printf("\n\n");
    printf("Enter 3 to Exit. ");
    printf("\n\n");
    scanf("%d", &menuNum); // reads number

    if (menuNum == 1) // If 1 is entered on the Menu...
    {
        printf("********************************\n");
        printf("\nYour New Password is: \n\n");

    // Each Password will Have 12 Characters(4 Uppercase letters, 4 Lowercase letters, 2 Numbers & 2 Symbols)

    for (i = 0; i < 4; ++i)
        password[j++] = 'a' + rand() % ('z' - 'a' + 1); // Generates 4 random Lowercase characters 

    for (i = 0; i < 4; ++i)
        password[j++] = 'A' + rand() % ('Z' - 'A' + 1); // Generates 4 random Uppercase characters

    for (i = 0; i < 2; ++i)
        password[j++] = '0' + rand() % ('0' - '9' + 1); // Generates 2 random numbers

    for (i = 0; i < 2; ++i)
        password[j++] = symbols[rand() % strlen(symbols)]; // Generates 2 random symbols

    password[j] = '\0';
    for(i = 0; i < sizeof(password)-1; ++i)
        {
        char c = password[i];
        j = rand() % len;
        password[i] = password[j];
        password[j] = c;
        } // Shuffles passwords Characters

    printf("%s\n\n", password);
    printf("********************************\n");
    fprintf(fp, "\n%s", password); // Outputs the Generated Passoword to the text file
    fclose(fp); // Closes the text file
    system("pause");
    }

    else if (menuNum == 2)
    {           
        printf("\nEnter your password for checking: ");
        printf("%s", passwordCheck);  // reads password
        if (strlen(passwordCheck) > 15) // Checks length of Password
        {
            printf("'%s' is too long. Needs to be less then 15 Characters\n", passwordCheck);
            system("pause");
        }
        else if (strlen(passwordCheck) < 9) //Checks length of Password
        {
            printf("'%s' is too short. Needs to be more then 9 Characters\n", passwordCheck);
            system("pause");
        }
    }

}

Answer 1

您应该一一读取文件中的所有字节并将字符保存在某种缓冲区中，直到遇到换行符。然后将缓冲区中的所有字节与您要添加的密码进行比较，如果相同，则该密码已经在文件中。清除缓冲区并读取直到下一个换行符。重复直到文件末尾。