假设我要求整数输入，例如scanf（＆＃34;％d＆＃34;，＆amp; integer）;.
我初始化了整数变量，如下所示：int integer;
问题 - 1：如果用户什么都没输入，我怎么知道？
问题 - 2：初始化整数变量（int integer;）后，整数包含什么？
答案 0 :(得分：2)
如果您没有输入任何内容，scanf将返回负值。
int integer;
int result = scanf("%d", &integer);
if (result > 0) { /* safe to use integer */ }
int integer;初始化为程序为其分配的位置的数据。因此它看起来像垃圾，应该使用合理的值进行初始化，例如0。
答案 1 :(得分：0)
来自：https://gcc.gnu.org/ml/gcc-help/2006-03/msg00101.html
for status in timeline:
if hasattr(status, 'quoted_status'):
print (status.quoted_status)
else:
print ("null")
如果想要使用/* --- self-identity --- */
#include "kbhit.h"
/* fileno setbuf stdin */
#include <stdio.h>
/* NULL */
#include <stddef.h>
/* termios tcsetattr tcgetattr TCSANOW */
#include <termios.h>
/* ioctl FIONREAD ICANON ECHO */
#include <sys/ioctl.h>
static int initialized = 0;
static struct termios original_tty;
int kbhit()
{
if(!initialized)
{
kbinit();
}
int bytesWaiting;
ioctl(fileno(stdin), FIONREAD, &bytesWaiting);
return bytesWaiting;
}
/* Call this just when main() does its initialization. */
/* Note: kbhit will call this if it hasn't been done yet. */
void kbinit()
{
struct termios tty;
tcgetattr(fileno(stdin), &original_tty);
tty = original_tty;
/* Disable ICANON line buffering, and ECHO. */
tty.c_lflag &= ~ICANON;
tty.c_lflag &= ~ECHO;
tcsetattr(fileno(stdin), TCSANOW, &tty);
/* Decouple the FILE*'s internal buffer. */
/* Rely on the OS buffer, probably 8192 bytes. */
setbuf(stdin, NULL);
initialized = 1;
}
/* Call this just before main() quits, to restore TTY settings! */
void kbfini()
{
if(initialized)
{
tcsetattr(fileno(stdin), TCSANOW, &original_tty);
initialized = 0;
}
}
----------------------------------
To use kbhit:
----------------- demo_kbhit.c -----------------
/* gcc demo_kbhit.c kbhit.c -o demo_kbhit */
#include "kbhit.h"
#include <unistd.h>
#include <stdio.h>
int main()
{
int c;
printf("Press 'x' to quit\n");
fflush(stdin);
do
{
if(kbhit())
{
c = fgetc(stdin);
printf("Bang: %c!\n", c);
fflush(stdin);
}
else usleep(1000); /* Sleep for a millisecond. */
} while(c != 'x');
}
----------------------------------
，则检查返回的值（而不是参数值。）如果返回的值为1，则用户输入整数值