filler.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <unistd.h>
/*
@brief 
- took help from stackoverflow/GFG for understanding the cammand line arguments concept argc, argv
- argc (ARGument Count) is an integer variable that stores the number of command-line arguments passed by the user including the name of the program. 
  So if we pass a value to a program, the value of argc would be 2 (one for argument and one for program name) 
- argv (ARGument Vector) is an array of character pointers listing all the arguments.
*/
#define PUSH_DATA _IOW('q', 2, struct queue_data)

struct queue_data{
    int length;
    char *data;
};

int main(int argc, char *argv[]){
    // ensuring right no. of arguments are being passed 
    if (argc != 2) {
        fprintf(stderr, "Usage: %s <string argument needed>\n", argv[0]);
        return EXIT_FAILURE;
    }
    printf("No. of arguments %d ", argc);
    char *data = argv[1];
    struct queue_data qd;
    qd.length = strlen(data) + 1;
    qd.data = data;

    int fd = open("/dev/shrish", O_RDWR);
    if (fd < 0){
        perror("Failed to open the device");
        return EXIT_FAILURE;
    }

    if (ioctl(fd, PUSH_DATA, &qd) < 0){
        perror("Failed to push data");
        close(fd);
        return EXIT_FAILURE;
    }

    printf("Data pushed successfully : %s\n", data);
    close(fd);
    return EXIT_SUCCESS;
}