我从来都不记得我是怎么做到的,因为它很少出现在我身上。但是在C或c++中,从标准输入中读取字符而不等待换行符(按enter)的最佳方法是什么?

理想情况下,它也不会将输入字符回显到屏幕上。我只是想在不影响控制台屏幕的情况下捕捉击键。


当前回答

下面是一个不向系统提供外壳的版本(在macOS 10.14上编写和测试)

#include <unistd.h>
#include <termios.h>
#include <stdio.h>
#include <string.h>

char* getStr( char* buffer , int maxRead ) {
  int  numRead  = 0;
  char ch;

  struct termios old = {0};
  struct termios new = {0};
  if( tcgetattr( 0 , &old ) < 0 )        perror( "tcgetattr() old settings" );
  if( tcgetattr( 0 , &new ) < 0 )        perror( "tcgetaart() new settings" );
  cfmakeraw( &new );
  if( tcsetattr( 0 , TCSADRAIN , &new ) < 0 ) perror( "tcssetattr makeraw new" );

  for( int i = 0 ; i < maxRead ; i++)  {
    ch = getchar();
    switch( ch )  {
      case EOF: 
      case '\n':
      case '\r':
        goto exit_getStr;
        break;

      default:
        printf( "%1c" , ch );
        buffer[ numRead++ ] = ch;
        if( numRead >= maxRead )  {
          goto exit_getStr;
        }
        break;
    }
  }

exit_getStr:
  if( tcsetattr( 0 , TCSADRAIN , &old) < 0)   perror ("tcsetattr reset to old" );
  printf( "\n" );   
  return buffer;
}


int main( void ) 
{
  const int maxChars = 20;
  char      stringBuffer[ maxChars+1 ];
  memset(   stringBuffer , 0 , maxChars+1 ); // initialize to 0

  printf( "enter a string: ");
  getStr( stringBuffer , maxChars );
  printf( "you entered: [%s]\n" , stringBuffer );
}

其他回答

ssinfod对Linux的回答的变体,对我的口味来说稍微干净一些,为wcout和wchar_t实现,并在没有错误的情况下擦除无效字符。

#include <functional>

//For Linux kbhit(). For Windows, use conio.h.
#ifdef __unix__
  #include <sys/ioctl.h> //For FIONREAD.
  #include <termios.h>

  //Call this at program start to setup for kbhit.
  void initTerminalInput()
  {
    //Disable internal buffering.
    std::wcout << std::unitbuf;

    //Turn off line buffering.
    struct termios term;
    tcgetattr(0, &term);
    term.c_lflag &= ~ICANON;
    tcsetattr(0, TCSANOW, &term);
    setbuf(stdin, NULL);
  }

  //Returns 0 if there's no input character to read.
  int kbhit()
  {
    static int nbbytes;
    ioctl(0, FIONREAD, &nbbytes);
    return nbbytes;
  }
#endif

//Waits for and retrieves a single validated character, calling a validation function on each character entered and
//erasing any that are invalid (when the validation function returns false).
static wchar_t getWChar(std::function<bool(wchar_t)> validationFunction)
{
  static wchar_t inputWChar;
  do
  {
    //Wait until there's an input character.
    while (!kbhit())
    {
    }
    inputWChar = getwchar();
    //Validate the input character.
    if (validationFunction(inputWChar))
    {
      //Valid.
      break;
    }
    else
    {
      //Erase the invalid character.
      std::wcout << L"\b \b";
    }
  } while (true);
  return inputWChar;
}

在下面的例子中,我想让用户输入1、2或3。输入的任何其他字符都不会显示,它将等待,直到按下其中一个有效字符:

int main()
{
  #ifdef __unix__
    initTerminalInput();
  #endif

  getWChar([] (wchar_t inputWChar)
  {
    return (inputWChar >= L'1' && inputWChar <= L'3');
  });

  return 0;
}

假设是Windows,看一下ReadConsoleInput函数。

我也遇到过同样的问题。这里是一个小的解决方案为windows控制台使用cygwing++与if(GetKeyState(keycode) & bitANDcompare){};

#include <windows.h>
#include <fstream>
#include <iostream>

using namespace std;
void clear() {
    COORD topLeft  = { 0, 0 };
    HANDLE console = GetStdHandle(STD_OUTPUT_HANDLE);
    CONSOLE_SCREEN_BUFFER_INFO screen;
    DWORD written;

    GetConsoleScreenBufferInfo(console, &screen);
    FillConsoleOutputCharacterA(
        console, ' ', screen.dwSize.X * screen.dwSize.Y, topLeft, &written
    );
    FillConsoleOutputAttribute(
        console, FOREGROUND_GREEN | FOREGROUND_RED | FOREGROUND_BLUE,
        screen.dwSize.X * screen.dwSize.Y, topLeft, &written
    );
    SetConsoleCursorPosition(console, topLeft);
}

class Keyclick{
    private:
    int key;
    char id;
    public:
    bool keydown = false;
    Keyclick(int key1, char id1){
        key=key1;
        id=id1;
    };
    void watch(){
        if(keydown==false){
            if(GetKeyState(key) & 0x8000 ){
                cout << id;
                cout << "  pressed.\r\n";
                keydown = true;
            }
        }
        if(keydown == true){
            if(!(GetKeyState(key) & 0x8000)) {
                cout << "released!!!!!!!!!!\r\n";
                keydown = false;
                clear();
            }
        }
    };
};

int main()
{
    bool primaryloop =true;
    Keyclick keysp(VK_SPACE,'S');
    Keyclick keyw(0x57,'w');
    Keyclick keya(0x41,'a');
    Keyclick keys(0x53,'s');
    Keyclick keyd(0x44,'d');
    Keyclick keyesc(VK_ESCAPE,'E');
    
    while(primaryloop){
        keysp.watch();
        keyw.watch();
        keya.watch();
        keys.watch();
        keyd.watch();
        keyesc.watch();
        
        if(keyesc.keydown){
            primaryloop=false;
        };      
    }
    return 0;
}

https://github.com/wark77/windows_console_keypoller/blob/main/getkeystate_SOLUTION01.cpp

下面是一个不向系统提供外壳的版本(在macOS 10.14上编写和测试)

#include <unistd.h>
#include <termios.h>
#include <stdio.h>
#include <string.h>

char* getStr( char* buffer , int maxRead ) {
  int  numRead  = 0;
  char ch;

  struct termios old = {0};
  struct termios new = {0};
  if( tcgetattr( 0 , &old ) < 0 )        perror( "tcgetattr() old settings" );
  if( tcgetattr( 0 , &new ) < 0 )        perror( "tcgetaart() new settings" );
  cfmakeraw( &new );
  if( tcsetattr( 0 , TCSADRAIN , &new ) < 0 ) perror( "tcssetattr makeraw new" );

  for( int i = 0 ; i < maxRead ; i++)  {
    ch = getchar();
    switch( ch )  {
      case EOF: 
      case '\n':
      case '\r':
        goto exit_getStr;
        break;

      default:
        printf( "%1c" , ch );
        buffer[ numRead++ ] = ch;
        if( numRead >= maxRead )  {
          goto exit_getStr;
        }
        break;
    }
  }

exit_getStr:
  if( tcsetattr( 0 , TCSADRAIN , &old) < 0)   perror ("tcsetattr reset to old" );
  printf( "\n" );   
  return buffer;
}


int main( void ) 
{
  const int maxChars = 20;
  char      stringBuffer[ maxChars+1 ];
  memset(   stringBuffer , 0 , maxChars+1 ); // initialize to 0

  printf( "enter a string: ");
  getStr( stringBuffer , maxChars );
  printf( "you entered: [%s]\n" , stringBuffer );
}

这在纯c++中以可移植的方式是不可能的,因为它太依赖于可能与stdin连接的终端(它们通常是行缓冲的)。不过,你可以使用一个库来实现:

conio available with Windows compilers. Use the _getch() function to give you a character without waiting for the Enter key. I'm not a frequent Windows developer, but I've seen my classmates just include <conio.h> and use it. See conio.h at Wikipedia. It lists getch(), which is declared deprecated in Visual C++. curses available for Linux. Compatible curses implementations are available for Windows too. It has also a getch() function. (try man getch to view its manpage). See Curses at Wikipedia.

如果你的目标是跨平台兼容性,我建议你使用curses。也就是说,我相信有一些函数可以用来关闭行缓冲(我相信这被称为“原始模式”,而不是“熟模式”-看看man stty)。如果我没记错的话,诅咒可以方便地帮你解决这个问题。