#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <sys/mman.h>

void
generate_progression(int *a, int a0, int d, int n)
{
    for (int i = 0; i < n; i++) {
        a[i] = a0 + i*d;
    }
}

int
main(int argc, const char * argv[])
{
    int n = atoi(argv[1]);
    int a0 = atoi(argv[3]);
    int d = atoi(argv[4]);
    int k = atoi(argv[5]);
    int *addr;
    int *a;
    a = calloc(n*k, sizeof(a));
    int fd;
    fd = open(argv[2], O_WRONLY | O_CREAT | O_APPEND, 0666);
    generate_progression(a, a0, d, k*n);
    addr = mmap(NULL, k*n*sizeof(k), PROT_WRITE | PROT_READ, MAP_ANON | MAP_SHARED, -1, 0);
    for (int i = 0; i < n; i++) {
        if (!fork()) {
            for (int j = 0; j < k; j++) {
                lseek(*addr, i*sizeof(i)+j*n*sizeof(j), SEEK_SET);
                write(*addr, &a[i+j*n], sizeof(a[i+j*n]));
            }
            exit(1);
        }
        wait(0);
    }
    wait(0);
    munmap(addr, k*n*sizeof(k));
    for (int i = 0; i < n*k*sizeof(n); i++) {
        write(fd, &addr[i], sizeof(char));
    }
    close(fd);
    return 0;
}