/*
 * nullfile.c
 *
 * 2000-02-06 Fredrik Roubert <fredrik_roubert@student.ethz.ch>
 * 2003-09-29 Fredrik Roubert <roubert@df.lth.se>
 * 2004-06-11 Fredrik Roubert <roubert@df.lth.se>
 *
 */

#if defined(__LONG_LONG_MAX__) || defined(sun)
# define _FILE_OFFSET_BITS 64
#endif

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>

static const unsigned char zero = 0;
static const char optstr[] = "hs:m:";

static void
usage(FILE *stream, const char *name)
{
	fprintf(stream, "Usage: %s [-s size] [-m mode] [file ...]\n", name);
}

int
main(int argc, char *argv[])
{
#if _FILE_OFFSET_BITS == 64
	unsigned long long size;
#else
	unsigned long size;
#endif
	unsigned long mode;
	const char *name;
	int fd, c, setmode;

	size = 0;
	mode = 0666;
	setmode = 0;

	for (; (c = getopt(argc, argv, optstr)) != EOF;)
		switch (c)
		{
			case 'h':
				usage(stdout, argv[0]);
				return EXIT_SUCCESS;

			case 's':
				errno = 0;
#if _FILE_OFFSET_BITS == 64
				size = strtoull(optarg, NULL, 0);
#else
				size = strtoul(optarg, NULL, 0);
#endif
				if (errno != 0)
				{
					perror(optarg);
					return EXIT_FAILURE;
				}
				break;

			case 'm':
				errno = 0;
				mode = strtoul(optarg, NULL, 8);
				if (errno != 0)
				{
					perror(optarg);
					return EXIT_FAILURE;
				}
				setmode = 1;
				break;

			case '?':
				usage(stderr, argv[0]);
				return EXIT_FAILURE;

			default:
				fprintf(stderr,
					"%s: Error parsing command line, "
					"getopt() returned 0x%02x\n",
					argv[0], c);
				return EXIT_FAILURE;
		}

	if (mode > 07777)
	{
		fprintf(stderr, "%s: %lo: Bad file mode\n", argv[0], mode);
		return EXIT_FAILURE;
	}

	if (optind == argc)
	{
		usage(stderr, argv[0]);
		return EXIT_FAILURE;
	}

	for (; optind < argc; optind ++)
	{
		name = argv[optind];

		if ((fd = open(name, O_WRONLY | O_CREAT | O_TRUNC, mode)) == -1)
		{
			perror(name);
			return EXIT_FAILURE;
		}

		if (setmode && fchmod(fd, mode) == -1)
		{
			perror(name);
			return EXIT_FAILURE;
		}

		if (size > 0)
		{
			if (size > 1)
			{
				if (lseek(fd, size - 1, SEEK_SET) == -1)
				{
					perror(name);
					return EXIT_FAILURE;
				}
			}

			if (write(fd, &zero, 1) == -1)
			{
				perror(name);
				return EXIT_FAILURE;
			}
		}

		if (close(fd) == -1)
		{
			perror(name);
			return EXIT_FAILURE;
		}
	}

	return EXIT_SUCCESS;
}