Question

我有2个程序，我希望1的输出是另一个的输入。像这样：

user@local:~/work/example$ ./feeder | parser

我的第一个程序如下：

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

int main()
{
    const char *buff[] = {
        "$GPRMC,173843,A,3349.896,N,11808.521,W,000.0,360.0,230108,013.4,E*69\r\n",
        "$GPGGA,111609.14,5001.27,N,3613.06,E,3,08,0.0,10.2,M,0.0,M,0.0,0000*70\r\n",
        "$GPGSV,2,1,08,01,05,005,80,02,05,050,80,03,05,095,80,04,05,140,80*7f\r\n",
        "$GPGSV,2,2,08,05,05,185,80,06,05,230,80,07,05,275,80,08,05,320,80*71\r\n",
        "$GPGSA,A,3,01,02,03,04,05,06,07,08,00,00,00,00,0.0,0.0,0.0*3a\r\n",
        "$GPRMC,111609.14,A,5001.27,N,3613.06,E,11.2,0.0,261206,0.0,E*50\r\n",
        "$GPVTG,217.5,T,208.8,M,000.00,N,000.01,K*4C\r\n"
    };

   int it;

    for(it = 0; it < 6; ++it)
    {
        fprintf(stdout, buff[it]);
        fflush(stdout);
        sleep(1);
    }

    return 0;
}

当我输入

user@local:~/work/example$ ./feeder | grep $

我确实看到输出每秒都会出现。

在我的解析器程序中，我有以下内容：

int main()
{
   while (1)
   {
       check_input()
   }
}

void check_input
{
    fd_set rfds;
    struct timeval tv;
    int retval;
    int n;
    char buff[MAX_BUFF];
    int descriptor=0;

    /* Watch cb to see when it has input. */
    FD_ZERO(&rfds);
    FD_SET(descriptor, &rfds);

    /* Wait up to five seconds. */
    tv.tv_sec = 5;
    tv.tv_usec = 0;

    retval = select(descriptor + 1, &rfds, NULL, NULL, &tv);

    /* Don't rely on the value of tv now! */

    if (retval == -1)
    {
        perror("select()");
    }
    else if (retval)
    {
//        printf("Data is available now.\n");
        if (FD_ISSET(0, &rfds))
        {
            n = read(0, buff, MAX_BUFF - 1);
            ... 
        }
    }
    else
        printf("No data within five seconds.\n");

}

问题是我的解析器程序有超时。似乎没有看到任何东西。有什么建议吗？

编辑1：描述符的值是0，例如STDIN_FILENO的值

无法在C中读取管道输出

0 个答案: