Tvheadend

#include <stdio.h>

#include <errno.h>

#include <signal.h>

#include <string.h>

#include <fcntl.h>

#include <unistd.h>

#include <stdlib.h>

#include <stdint.h>

#include <time.h>

#include <assert.h>

#include <sys/ioctl.h>

#include <linux/dvb/frontend.h>

static int fd = 0;

static char* program_name = "?";

static char* device = "?";

void cleanup(int signal_number) {

    if (fd != 0) {

        if (close(fd) != 0) {

            fprintf(stderr, "%s: error closing %s: %s\n", program_name, device, strerror(errno));

            exit(2);

        }

    }

    exit(0);

}

int main(int argc, char* argv[]) {

    program_name = argv[0];

    if (argc != 2) {

        fprintf(stderr, "usage: %s device\n", program_name);

        return 1;

    }

    device = argv[1];

    {

        static struct dtv_property properties[] = {

            { .cmd = DTV_STAT_CNR }

        };

        static struct dtv_properties properties_request = {

            .num = sizeof(properties) / sizeof(properties[0]),

            .props = properties

        };

        (void) signal(SIGINT, cleanup);

        (void) signal(SIGTERM, cleanup);

        (void) signal(SIGHUP, cleanup);

        fd = open(device, O_RDONLY);

        if (fd < 1) {

            fprintf(stderr, "%s: cannot open %s: %s\n", program_name, device, strerror(errno));

            return 2;

        }

        while (ioctl(fd, FE_GET_PROPERTY, &properties_request) == 0) {

            unsigned scale = properties[0].u.st.stat[0].scale;

            time_t current_time = time(NULL);

            char current_time_string[1024];

            assert(strftime(current_time_string, sizeof(current_time_string), "%H:%M:%S", localtime(&current_time)) > 0);

            printf("%s SNR: new=", current_time_string);

            switch (scale) {

            case FE_SCALE_NOT_AVAILABLE:

                printf("N/A");

                break;

            case FE_SCALE_DECIBEL:

                printf("%.3f dB", properties[0].u.st.stat[0].svalue / 1000.0);

                break;

            case FE_SCALE_RELATIVE:

                printf("%.1f %%", properties[0].u.st.stat[0].uvalue / 65535.0 * 100);

                break;

            default:

                printf("(determination failed, unexpected scale %d)\n", scale);

            }

            {

                uint16_t snr; 

                if (ioctl(fd, FE_READ_SNR, &snr) == 0) {

                    printf(", old=%d\n", snr);

                }

                else {

                    printf(", old=(failed, error on ioctl FE_READ_SNR: %s)\n", strerror(errno));

                }

            }

            sleep(1);

        }

        fprintf(stderr, "%s: error on ioctl FE_GET_PROPERTY: %s\n", program_name, strerror(errno));

        cleanup(0);

    }

    return 0;

}