#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <assert.h>
#include <signal.h>


#define	LOGFILE_BUF_LEN		65536

int do_rotate = 0;

void
signal_hup(int unused)
{
	do_rotate = 1;
}


int
main(int argc, char *argv[])
{
	int t;
	int fd, r;
	char buf[LOGFILE_BUF_LEN];

	if (argc < 2) {
		printf("Error: usage: %s <logfile>\n", argv[0]);
		exit(1);
	}

	fd = open(argv[1], O_WRONLY |  O_APPEND | O_CREAT, 0644);
	if (fd < 0) {
		perror("open");
		exit(1);
	}

	signal(SIGHUP, signal_hup);

	setbuf(stdin, NULL);
	setbuf(stdout, NULL);
	close(2);
	t = open("/dev/null", O_RDWR);
	assert(t > -1);
	dup2(t, 2);

	while( (r = read(0, buf, LOGFILE_BUF_LEN)) > 0) {
		if (write(fd, buf, r) != r) {
			perror("write");
			break;
		}
		fsync(fd);

		/* Check for rotate (which is really just 'reopen') */
		if (do_rotate == 1) {
			do_rotate = 0;
			close(fd); fd = -1;
			fd = open(argv[1], O_WRONLY |  O_APPEND | O_CREAT, 0644);
			if (fd < 0) {
				perror("open");
				exit(1);
			}
		}
	}
	close(fd); fd = -1;
	exit(0);
}