替換獲取（）與fgets（）

Question

我一直在測試這個結構，我得到關於使用gets的警告。有人提到用fgets代替，並用'\0'代替。任何建議如何改變我的代碼來做到這一點？

void regCars(Car reg[], int *pNrOfCars) { 
    char again[WORDLENGTH] = "yes", model[WORDLENGTH], tmp[WORDLENGTH]; 
    int year, milage; 

    while (strcmp(again, "yes") == 0) { 
     printf("Enter model:"); 
     gets(model); 
     printf("Enter Year:"); 
     gets(tmp); 
     year = atoi(tmp); 
     printf("Enter milage:"); 
     gets(tmp); 
     milage = atoi(tmp); 
     reg[*pNrOfCars] = createCar(model, year, milage); 
     (*pNrOfCars)++; 
     printf("Continue? (yes/no)"); 
     gets(again); 
    } 
} 

Answer 1

您可以編寫一個效用函數mygets()是需要兩個參數：一個指向目標數組，其大小：

char *mygets(char *dest, size_t size) { 
    /* read a line from standard input and strip the linefeed if any */ 
    if (fgets(dest, size, stdin)) { 
     dest[strcspn(dest, "\n")] = '\0'); 
     return dest; 
    } 
    return NULL; 
} 

void regCars(Car reg[], int *pNrOfCars) { 
    char model[WORDLENGTH], tmp[WORDLENGTH]; 
    int year, milage; 

    for (;;) { 
     printf("Enter model:"); 
     if (!mygets(model, sizeof mode)) 
      break; 
     printf("Enter year:"); 
     if (!mygets(tmp, sizeof tmp)) 
      break; 
     year = atoi(tmp); 
     printf("Enter milage:"); 
     if (!mygets(tmp, sizeof tmp)) 
      break; 
     milage = atoi(tmp); 
     reg[*pNrOfCars] = createCar(model, year, milage); 
     (*pNrOfCars)++; 
     printf("Continue? (yes/no)"); 
     if (!mygets(tmp, sizeof(tmp)) 
      break; 
     if (strcmp(again, "yes") != 0) 
      break; 
    } 
} 

注意，您可以用prompt()功能輸出的因式分解更多的代碼提問並讀取響應：

char *prompt(const char *message, char *dest, size_t size) { 
    printf("%s ", message); 
    fflush(stdout); 
    /* read a line from standard input and strip the linefeed if any */ 
    if (fgets(dest, size, stdin)) { 
     dest[strcspn(dest, "\n")] = '\0'); 
     return dest; 
    } 
    return NULL; 
} 

void regCars(Car reg[], int *pNrOfCars) { 
    char model[WORDLENGTH], tmp[WORDLENGTH]; 
    int year, milage; 

    for (;;) { 
     if (!prompt("Enter model:", model, sizeof mode)) 
      break; 
     if (!prompt("Enter year:", tmp, sizeof tmp)) 
      break; 
     year = atoi(tmp); 
     if (!prompt("Enter milage:", tmp, sizeof tmp)) 
      break; 
     milage = atoi(tmp); 
     reg[*pNrOfCars] = createCar(model, year, milage); 
     (*pNrOfCars)++; 
     if (!prompt("Continue? (yes/no)", tmp, sizeof(tmp)) 
      break; 
     if (strcmp(again, "yes") != 0) 
      break; 
    } 
} 

另請注意，此功能應取大小爲reg數組在停止提示時輸入更多數據。按照當前規定，它具有與gets()相同的缺點，意外的輸入會導致未定義的行爲。

Answer 2

只是做例如

if (NULL != fgets(model, WORDLENGTH, stdin)) /* Read the string. */ 
{ 
    model[strcspn(model, "\r\n")] = '\0'; /* Cut off \n and/or \r, if any. */ 
} 

Answer 3

這是一個小一點小技巧比它的外觀。用fgets（）替換get就沒有太大的意義，如果你在超長輸入中處理一個截斷的行並將其作爲有效處理。你只是用錯誤的行爲取代了未定義的行爲。

if(fgets(line, sizeof(line), fp)) 
{ 
    if(!strchr(line, '\n')) 
    { 
     /* line is too long, what you do is up to you, but normally 
     we will discard it */ 
     int ch; 

     while((ch = fgetc(fp)) != EOF) 
     if(ch == '\n') 
      break; 

    } 
    else 
    { 
     /* line is a normal line with a trailing '\n' (gets trims the '\n')   */ 
    } 
}