message_reader.c

#include "message_slot.h"

#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>

int main(int argc, char* argv[]) {
    int file_desc, ret_val, index, length;
    char buffer[BUF_SIZE];

    if (argc < 2) {
        printf("Invalid Arguments: Not enough arguments\n");
        exit(-1);
    }

    ret_val = sscanf(argv[1], "%d", &index);
    if (ret_val < 1 || index < 0 || index > 3) {
        printf("Invalid Arguments: invalid index\n");
        exit(-1);
    }

    file_desc = open("/dev/"DEVICE_FILE_NAME, O_RDONLY);
    if (file_desc < 0) {
        printf("Error: Can't open device file: %s. %s \n", DEVICE_FILE_NAME, strerror(errno));
        exit(-1);
    }

    ret_val = ioctl(file_desc, IOCTL_SET_ENC, index);

    if (ret_val < 0) {
        printf("Error: ioctl_set_msg failed: %d. %s\n", ret_val, strerror(errno));
        close(file_desc);
        exit(-1);
    }

    length = read(file_desc, buffer, BUF_SIZE);

    close(file_desc);

    printf("Read from message slot: %s\n", buffer);
    return 0;
}