fallocate.c

#define _GNU_SOURCE
#include <fcntl.h>	// open
#include <stdlib.h>	// fallocate
#include <stdio.h>

inline void err(const char *msg){
	perror(msg);
	exit(1);
}

off_t const size = 1024 * 1024 * 1024;

int main(void){
	int fd = open("testfile", O_RDWR | O_TRUNC | O_CREAT, 0644);

	if (fd < 0)
		err("open");

	if (fallocate(fd, FALLOC_FL_ZERO_RANGE, 0, 8 * size) < 0)
		err("fallocate");
}