#define _POSIX_C_SOURCE 200112L

#include <stdio.h>

#include <unistd.h>

#include <sys/types.h>

#include <stdlib.h>

#include <errno.h>

#include <sys/mman.h>

#define SIZE 1080*4*1920*4*3

__attribute__((noreturn))

void fail (const char *const msg) {

perror(msg);

exit(-errno);

}

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

FILE *out;

char *buf;

if (NULL == (out = fopen("output.rgb", "w+")))

fail("Failed to fopen");

if (0 != ftruncate(fileno(out), SIZE))

fail("Failed to create file");

buf = mmap(NULL, SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fileno(out), 0);

if (MAP_FAILED == buf)

fail("Failed to mmap");

// use buf as if it was buf = malloc(SIZE)

munmap(buf, SIZE);

fclose(out);

return 0;

}