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

	int i;
	for (i = 1; i < argc; i++) {
		if (argv[i][0] != '-')
			break;

		else if (!strncmp(argv[i], "-s=", 3))
			s_size = atoi(argv[i] + 3);

		else if (!strcmp(argv[i], "-c"))
			c_flag = 1;

		else if (!strcmp(argv[i], "--help")) {
			printf("truncate [-c Do not create files] [-s=SIZE] file1 file2...\n");
			return 0;
		}
	}

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

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

	close(fd);
	return 0;
}