micro-utils/coreutils/truncate.c

#include <fcntl.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>

int main(int argc, char **argv) {
	unsigned int c_flag = 0;
	unsigned int s_size = 0;

	int opt;
	while ((opt = getopt(argc, argv, "s:c")) != -1) {
		switch (opt) {
			case 's':
				s_size = atoi(optarg);
				break;

			case 'c':
				c_flag = 1;
				break;

			default:
				printf("truncate [file]\n\t[-c Do not create files] [-s=SIZE]\n");
				return 0;
		}
	}

	argv += optind;
	argc -= optind;

	if (argc == 0) {
		fprintf(stderr, "truncate: missing operand\n");
		return 1;
	}

	int flags = O_WRONLY | O_NONBLOCK;
	if (!c_flag)
		flags |= O_CREAT;

	int fd = open(argv[0], flags, 0666);
	if (fd < 0) {
		fprintf(stderr, "truncate %s %s\n", argv[0], strerror(errno));
		return 1;
	}

	if (ftruncate(fd, s_size) == -1) {
		close(fd);
		fprintf(stderr, "truncate %s %s\n", argv[0], strerror(errno));
		return 1;
	}

	close(fd);
	return 0;
}