c - 我如何处理 C 中的字符串输入？

Question

我只是在练习 C，我想制作一个带有用户名和密码的简单登录程序...这是我的代码:

int main(){
   char uname, passwd;

   printf("Enter your username: ");
   scanf("%c", uname);
   printf("Enter your password: ");
   scanf("%c", passwd);

   printf(" \n");

   if (uname == "waw" && passwd == "wow"){
      printf("You have logged in\n");
   } else {
      printf("Failed, please try again\n");
   }
   return 0;
}

然后我在尝试编译它时遇到了这个错误

log.c: In function ‘main’:
log.c:7:10: warning: format ‘%c’ expects argument of type ‘char *’, but     argument 2 has type ‘int’ [-Wformat=]
    scanf("%c", uname);
          ^
log.c:9:10: warning: format ‘%c’ expects argument of type ‘char *’, but     argument 2 has type ‘int’ [-Wformat=]
    scanf("%c", passwd);
          ^
log.c:13:14: warning: comparison between pointer and integer
    if (uname == "waw" && passwd == "wow"){
              ^
log.c:13:33: warning: comparison between pointer and integer
    if (uname == "waw" && passwd == "wow"){
                                 ^

Answer 1

1) 不要读入(扫描)一个字符。你需要一个字符串。使用格式说明符 %s 而不是 %c

2) 使用strcmp比较字符串值

试试这个:

#include <stdio.h>

int main(){
   int res;
   char uname[40];   // char arrays instead of single char
   char passwd[40];

   printf("Enter your username: ");
   res = scanf("%39s", uname);  // Set a maximum number of chars to read to
                                // 39 to avoid overflow
   if (res != 1) exit(1);       // Error on stdin. End program

   printf("Enter your password: ");
   res = scanf("%39s", passwd);
   if (res != 1) exit(1); // Error on stdin

   printf(" \n");

   // Use strcmp to compare values of two strings.
   // If strcmp returns zero, the strings are identical
   if ((strcmp(uname, "waw") == 0) && (strcmp(passwd, "wow") == 0)){
       printf("You have logged in\n");
   } else{
       printf("Failed, please try again\n");
   }
   return 0;
}