#include <unistd.h>
#include <fcntl.h>
#include <stdio.h>

#define BUFF_SIZE 4096

int open_files(int count, char **names, int* fd)
{
	int res = count, i;
	for (i = 0; i < count; i++)
	{
		if ((fd[i] = open(names[i], O_RDONLY)) == -1 || 
				(fd[i] != -1 && lseek(fd[i], 0, SEEK_END) == -1))
		{
			fd[i] = -1;
			perror(names[i]);
			res --;
		}
	}
	return res;
}

void check_loop(int *fd, int file_count, char **fnames)
{
	static char buffer[BUFF_SIZE];
	int i, j;
	while(1)
	{
		for (i = 0; i < file_count; i++)
		{
			if (fd[i] != -1)
			{
				int filesize = lseek(fd[i], 0, SEEK_END);
				if (filesize > (1024 << 6))
				{
					lseek(fd[i], -BUFF_SIZE, SEEK_END);
					int read_bytes = read(fd[i], buffer, BUFF_SIZE);
					int pos[2], ind = 0;
					for (j = read_bytes - 1; j >= 0 && ind < 2; j--)
					{
						if (buffer[j] == '\n')
						{
							pos[ind++] = j;
						}
					}
					int tmpfd = open(fnames[i], O_TRUNC | O_WRONLY);
					write(tmpfd, &buffer[pos[1] + 1], pos[0] - pos[1]);
					close(tmpfd);
				}
			}
		}
		sleep(5);
	}
}

int main(int argc, char *argv[])
{
	int i;
	int fd[argc];
	if (open_files(argc - 1, argv + 1, fd))
	{
		check_loop(fd, argc - 1, argv + 1);
	}
	return 0;
}