Makes a big file.

mkbigfile.c

#include <sys/stat.h>
#include <fcntl.h>
#include <inttypes.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

void usage();

int main(int argc, char **argv) {
	FILE *fp;
	int fd;
	char *filename;
	int sizeGb, c, ret;
	uintptr_t size, i;
	bool quiet;
	
	/* Defaults! */
	filename = NULL;
	size = sizeGb = 0;
	quiet = false;

	/* Get the filename and the number of gigs to write */
	while ((c = getopt(argc, argv, "qf:s:h")) != -1) {
		switch (c) {
			case 'f':
				filename = strdup(optarg);
				break;
			case 's':
				sizeGb = atoi(optarg);
				size = sizeGb * 1024L * 1024L * 1024L;
				break;
			case 'q':
				quiet = true;
				break;
			case 'h':
			default:
				usage();
		}
	}
	
	/* Make sure we got the arguments */
	if (sizeGb < 1 || size < 1 || NULL == filename) {
		usage();
	}

	/* Tell the user what we're doing */
	if (false == quiet) {
		printf("Writing %dGB (%" PRIiPTR " bytes) file, \"%s\"\n", sizeGb, size, filename);
	}

	/* Write a large file */
	fp = fopen(filename, "wb+");
	for (i = 0; i < size; i++) {
		fprintf(fp, "%c", '\0');
	}
	fclose(fp);
	
	/*
	fp = fopen(filename, "wb+");
	fseek(fp, size, SEEK_SET);
	fputc(0, fp);
	fclose(fp);
	//*/
	
	/*
	fd = creat(filename, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
	ret = ftruncate(fd, size);
	if (0 != ret) {
		fprintf(stderr, "Error creating file");
		return EXIT_FAILURE;
	}
	close(fd);
	*/

	/* Bye */
	free(filename);
	return EXIT_SUCCESS;
}

void usage() {
	printf("usage: mkbigfile [-q] -f <filename> -s <size (GB)>\n");
	printf("\t-q\tquiet\n");
	printf("\t-f\tfilename to write to\n");
	printf("\t-s\tnumber of gigs to write\n");
	exit(EXIT_FAILURE);
}