Add initial version of hwclock(8)

Makefile

@@ -3,7 +3,7 @@ include config.mk
 .POSIX:
 .SUFFIXES: .c .o
 
-HDR = arg.h config.def.h proc.h reboot.h util.h
+HDR = arg.h config.def.h proc.h reboot.h rtc.h util.h
 LIB = \
 	util/agetcwd.o        \
 	util/apathmax.o       \
@@ -29,6 +29,7 @@ SRC = \
 	free.c              \
 	getty.c             \
 	halt.c              \
+	hwclock.c           \
 	id.c                \
 	insmod.c            \
 	killall5.c          \

hwclock.c

@@ -0,0 +1,106 @@
+/* See LICENSE file for copyright and license details. */
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <sys/stat.h>
+#include <sys/time.h>
+#include <sys/types.h>
+#include <time.h>
+#include <unistd.h>
+#include "rtc.h"
+#include "util.h"
+
+static void echotime(char *);
+static void readrtctm(struct tm *, int);
+static void writertctm(struct tm *, int);
+static void writetime(char *);
+
+static void
+usage(void)
+{
+	eprintf("usage: %s [-rw] [-u]\n", argv0);
+}
+
+int
+main(int argc, char *argv[])
+{
+	char *dev = "/dev/rtc";
+	int rflag = 0;
+	int wflag = 0;
+
+	ARGBEGIN {
+	case 'r':
+		rflag = 1;
+		break;
+	case 'w':
+		wflag = 1;
+		break;
+	case 'u':
+		break;
+	default:
+		usage();
+	} ARGEND;
+
+	if ((rflag ^ wflag) == 0)
+		eprintf("missing or incompatible function\n");
+
+	/* Only UTC support at the moment */
+	setenv("TZ", "UTC0", 1);
+	tzset();
+
+	if (rflag == 1)
+		echotime(dev);
+	else if (wflag == 1)
+		writetime(dev);
+
+	return EXIT_SUCCESS;
+}
+
+static void
+echotime(char *dev)
+{
+	struct tm tm;
+	time_t t;
+	int fd;
+
+	fd = open(dev, O_RDONLY);
+	if (fd < 0)
+		eprintf("open %s:", dev);
+	readrtctm(&tm, fd);
+	t = mktime(&tm);
+	printf("%s", asctime(localtime(&t)));
+	close(fd);
+}
+
+static void
+readrtctm(struct tm *tm, int fd)
+{
+	memset(tm, 0, sizeof(*tm));
+	ioctl(fd, RTC_RD_TIME, tm);
+}
+
+static void
+writertctm(struct tm *tm, int fd)
+{
+	ioctl(fd, RTC_SET_TIME, tm);
+}
+
+static void
+writetime(char *dev)
+{
+	struct timeval tv;
+	struct tm *tm;
+	time_t t;
+	int fd;
+
+	fd = open(dev, O_WRONLY);
+	if (fd < 0)
+		eprintf("open %s:", dev);
+	gettimeofday(&tv, NULL);
+	t = tv.tv_sec;
+	tm = gmtime(&t);
+	writertctm(tm, fd);
+	close(fd);
+}

rtc.h

@@ -0,0 +1,2 @@
+#define RTC_RD_TIME	_IOR('p', 0x09, struct tm) /* Read RTC time   */
+#define RTC_SET_TIME	_IOW('p', 0x0a, struct tm) /* Set RTC time    */