將 bin 文件中的字符串轉換為 fgets() 字符串

Question

在我的代碼中，我創建了 3 個新文件。

如果文件“用戶”不存在，我會創建一個包含一些信息來初始化文件的文件。

之后，我想使用 fgets() 函數比較來自用戶的字符串，然后將字符串與文件中的字符串（密碼和 ID）進行比較，您可以在代碼的開頭看到 struct: user。 現在，當我使用“strcmp”時，它總是給我“1”。

enter code here

#define CRT_SECURE_NO_WARNINGS
#pragma warning(disable:4996)
#include <stdio.h>
#include <stdbool.h>
#include <time.h>
#include "doubly_list.h"

typedef struct user {
    int SecurityLevel;
    char ID[15];
    char Password[15];
    char FullName[20];
}user;

typedef struct items {
    char movie_name[20];
    char producer_name[20];
    int release_date_year, release_date_month, release_date_day;
    float rating;
    int serial_number;
    bool is_adult_video;
}items;

void main()
{
    char id_input[15], password_input[15];
    int day, month, year, hours, mins, SecurityLevel;


FILE* log;
log = fopen("log.txt", "a");
fclose(log);

FILE* users;
users = fopen("users.dat", "rb+");

user new_user;
if (users == NULL)
{
    FILE* users;
    users = fopen("users.dat", "ab+");
    new_user.SecurityLevel = 3;
    strcpy(&new_user.Password, "admin");
    strcpy(&new_user.ID, "admin");
    strcpy(&new_user.FullName, "System_Manager");
    fwrite(&new_user, sizeof(new_user), 1, users);
    fclose(users);
}


FILE* item;
item = fopen("users.dat", "ab+");
fclose(item);

        printf("Enter ID: ");
        fgets(id_input, 15, stdin);
        flushall();
        printf("Enter Password : ");
        fgets(password_input, 15, stdin);

        log = fopen("log.txt", "a+");
        fprintf(log, "\nthe user entered the ID : %s", id_input);
        fprintf(log, "the user entered the password : %s", password_input);

        FILE* users_out= fopen("users.dat", "rb");
        fread(&new_user, sizeof(user), 1, users_out);

        int result= result = strcmp(password_input, new_user.Password);
        printf("\n%d\n", result);

        if (strcmp(password_input, new_user.Password)==0)
            printf("\nLog in was successful.....\n\n");
        else
            printf("\nLog In was Unseccessful.....\n\n");

        fclose(log);
        fclose(users_out);

system("pause");
}

Answer 1

代碼使用fgets()並且無法刪除尾隨'\\n' 。 然后輸入緩沖區至少 1 太小

printf("Enter ID: ");
fgets(id_input, 15, stdin); // likely has \n in `id_input`.

而是考慮一個輔助函數，例如

// read a line of input
// 1: Success
// 0: bad input
// EOF: end-of-file or rare input error
int read_line80(const char *prompt, char *dest, size_t sz) {
  char buf[80 * 2]; // Be generous to allow for casual over long input
  // If VLAs allowed, consider `char buf[sz + 2];`

  if (prompt) fputs(prompt, stdout);
  fflush(stdout);  // Make certain output seen before input

  if (sz > 0) dest[0] = '\0';
  if (fgets(buf, sizeof buf, stdin) == NULL) return EOF;

  size_t len = strlen(buf);
  if (len > 0 && buf[len-1] == '\n') {
    buf[--len] = '\0';
  }

  // Maybe add extra code here to see if `fgets()` did not read everything

  if (len >= sz) return 0;
  strcpy(dest, buf);
  return 1;
}

然后

    if (read_line("Enter ID: ", id_input, sizeof id_input == 1) &&
        read_line("Enter Password : ", password_input, sizeof password_input == 1)) {
      // Oh happy day!
      // Use input
    } else {
      // Fail
    } 

關鍵是用戶輸入是邪惡的，最好在輔助函數中讀取一行輸入並讓它處理 I/O 細微差別。 讓調用代碼專注於輸入的非 I/O 方面。