#include <stdio.h>
#include <stdlib.h>
#include <string.h>

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

int main(int argc, char **argv)
{
	int fd;         /* File descriptor. */
	int len;        /* Length of data read from file. */

	/* Ensure we have a file to open. */
	if (argc < 2)
		return 1;

	/* Try to open the file. */
	fd = open(argv[1], O_RDONLY, 0);
	/* Exit if open failed. */
	if (fd == -1)
		return 1;

	if (argc == 2) {
		/* Just print out the file length. */
		char mesg[16];
		int len = lseek(fd, 0, SEEK_END); /* Get the length of the file. */
		sprintf(mesg, "%i\n", len);       /* Format number as a string. */
		write(1, mesg, strlen(mesg));
		return 0;
	} else {
		/* Read and print out the byte at the specified offset. */
		char buf[2];
		int offset = atoi(argv[2]);  /* Offset from which to read a byte. */
		lseek(fd, offset, SEEK_SET); /* Seek to that offset. */
		len = read(fd, buf, 1);      /* Try to read a byte. */
		if (len == 1) {
			/* Byte read successful. */
			buf[1] = '\n'; /* Include a newline when printing out. */
			write(1, buf, 2);
			return 0;
		} else {
			/* Byte read failed. */
			const char *mesg = "Readn't\n";
			write(1, mesg, strlen(mesg));
			return 1;
		}
	}
}