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(138条消息) 嵌入式linux:getchar() 非阻塞_起点的博客-CSDN博客_getchar 非阻塞

程序

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//由于getchar() 函数会一直阻塞，网上搜到下面的函数来实现非阻塞的读取。实际使用的时候只需要调用kbhit() 函数即可。其他函数没有看是什么意思
#include <stdio.h>
#include <string.h>
#include <sys/time.h>
#include <sys/types.h>
#include <unistd.h>
#include <termios.h>
#include <unistd.h>

static struct termios ori_attr, cur_attr;

static __inline int tty_reset(void)
{
    if (tcsetattr(STDIN_FILENO, TCSANOW, &ori_attr) != 0)
        return -1;

    return 0;
}

static __inline int tty_set(void)
{

    if (tcgetattr(STDIN_FILENO, &ori_attr))
        return -1;

    memcpy(&cur_attr, &ori_attr, sizeof(cur_attr));
    cur_attr.c_lflag &= ~ICANON;
    //        cur_attr.c_lflag |= ECHO;
    cur_attr.c_lflag &= ~ECHO;
    cur_attr.c_cc[VMIN] = 1;
    cur_attr.c_cc[VTIME] = 0;

    if (tcsetattr(STDIN_FILENO, TCSANOW, &cur_attr) != 0)
        return -1;

    return 0;
}

static __inline int kbhit(void)
{

    fd_set rfds;
    struct timeval tv;
    int retval;

    /* Watch stdin (fd 0) to see when it has input. */
    FD_ZERO(&rfds);
    FD_SET(0, &rfds);
    /* Wait up to five seconds. */
    tv.tv_sec = 0;
    tv.tv_usec = 0;

    retval = select(1, &rfds, NULL, NULL, &tv);
    /* Don't rely on the value of tv now! */

    if (retval == -1)
    {
        perror("select()");
        return 0;
    }
    else if (retval)
        return 1;
    /* FD_ISSET(0, &rfds) will be true. */
    else
        return 0;
    return 0;
}

int main()
{
    int tty_set_flag;
    tty_set_flag = tty_set();
    while (1)
    {

        if (kbhit())
        {
            const int key = getchar();
            printf("%c pressed\n", key);
            if (key == 'q')
                break;
        }
        else
        {
            fprintf(stderr, "<no key detected>\n");
        }
    }

    if (tty_set_flag == 0)
        tty_reset();
    return 0;
}
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#include <stdio.h>
#include <termios.h>
#include <unistd.h>
#include <fcntl.h>

int kbhit(void)
{
    struct termios oldt, newt;
    int ch;
    int oldf;
    tcgetattr(STDIN_FILENO, &oldt);
    newt = oldt;
    newt.c_lflag &= ~(ICANON | ECHO);
    tcsetattr(STDIN_FILENO, TCSANOW, &newt);
    oldf = fcntl(STDIN_FILENO, F_GETFL, 0);
    fcntl(STDIN_FILENO, F_SETFL, oldf | O_NONBLOCK);
    ch = getchar();
    tcsetattr(STDIN_FILENO, TCSANOW, &oldt);
    fcntl(STDIN_FILENO, F_SETFL, oldf);

    if (ch != EOF)
    {
        ungetc(ch, stdin);
        return 1;
    }

    return 0;
}

int main(void)

{
    while(1)
    {
        if(kbhit())
        {
            printf("keyboard hit\n");
            printf("%c\n", getchar());
        }
        else
        {
            printf("keyboard not hit\n");
        }
    }

    return 0;
}