C - 有没有办法读取用户输入的单个字符，而不是将其余字符"pushed down"到下一个输入请求？

Question

所以，我正在用C语言开发一个简单的刽子手游戏，我有函数read_guess，如下所示。

void read_guess(char *guesses, char *p_current_guess)
{
int valid_guess = 0;
// Repeatedly takes input until guess is valid
while (valid_guess == 0)
{
printf(">>> ");
fgets(p_current_guess, 2, stdin);
if (!isalpha(*p_current_guess)) printf("Guesses must be alphabetic. Please try again.nn");
else
{
valid_guess = 1;
// Iterates over array of guesses and checks if letter has already been guessed
for (int i = 0; guesses[i] != ''; i++)
{
if (guesses[i] == *p_current_guess)
{
printf("You have already guessed this letter. Please try again.nn");
valid_guess = 0;
break;
}
}
}
}
}

我已经尝试了所有标准输入函数(包括getchar(，但是对于所有这些函数，当提供大于一个字符的输入时，而不是只取第一个字符并继续前进(或再次询问(，其余的输入被"推回"，下次请求输入时，无论是因为输入包含非字母字符还是下一轮开始， 其余输入将自动处理。这将对输入的每个字符重复。

我怎样才能避免这种情况？

Answer 1

您正在使用fgets这很好，但不幸的是不是正确的方法...

fgets读取到行尾或最多比请求的字符数少 1个。当然，剩余的字符留给下一个读取操作...

惯用的方法是确保阅读到行尾，无论长度如何，或者至少达到更大的长度。

1. 简单，但输入时可能会失败超过 SIZE 字符：

   #define SIZE 64
   ...
   void read_guess(char *guesses, char *p_current_guess)
   {
   char line[SIZE];
   int valid_guess = 0;
   // Repeatedly takes input until guess is valid
   while (valid_guess == 0)
   {
   printf(">>> ");
   fgets(line, SiZE, stdin);                // read a line of size at most SIZE-1
   p_current_guess[0] = line[0];            // keep first character
   p_current_guess[1] = '';
   ...
   

2. 坚固但稍微复杂一些

   /**
   * Read a line and only keep the first character
   *
   * Syntax: char * fgetfirst(dest, fd);
   *
   * Parameters:
   *  dest: points to a buffer of size at least 2 that will recieve the
   *         first character followed with a null
   *  fd  : FILE* from which to read
   *
   * Return value: dest if one character was successfully read, else NULL
   */
   char *readfirst(dest, fd) {
   #define SIZE 256              // may be adapted
   char buf[SIZE];
   char *cr = NULL;          // return value initialized to NULL if nothing can be read
   for (;;) {
   if(NULL == fgets(buff, sizeof(buff), fd)) return cr; // read error or end of file
   if (0 == strcspn(buff, "n")) return cr;             // end of file
   if (cr == NULL) {                                    // first read:
   cr = dest;                        //  prepare to return first char
   dest[0] = buff[0];
   dest[1] = 0;
   }
   }
   }
   

   然后，您可以在代码中简单地使用它：

   void read_guess(char *guesses, char *p_current_guess)
   {
   int valid_guess = 0;
   // Repeatedly takes input until guess is valid
   while (valid_guess == 0)
   {
   printf(">>> ");
   fgetfirst(p_current_guess, stdin);
   

Answer 2

每次要请求输入时，都可以丢弃所有输入，直到行尾。

void skip_to_eol(FILE* f, int c)
{
while (c != EOF && c != 'n')
c = fgetc(f);
}
...
char c = getchar(); // instead of fgets
skip_to_eol(stdin, c);

Answer 3

你可以在 windows 上使用 getch(( 函数来获取单个字符。 这是Linux等效

的Linux 中的 getch(( 和 getche(( 等价于什么？