Reschedule when time moved backwards

2 files changed, 8 insertions, 0 deletions

diff --git a/README.md b/README.md
index 4b6832c..29e0ca9 100644
--- a/README.md
+++ b/README.md
@@ -127,6 +127,7 @@ Only mtime is looked at, so touch(1) is good.
   execs the command.  You need to ensure (by setting up supervision)
   snooze runs again after that!
 * if we woke due to a SIGALRM, the command is executed immediately as well
+* if we notice time moved backwards, recompute the time until the event
 * if the event is in the future, recompute the time it takes, possibly
   considering shifting of the system time or timezone changes
   (timezone reload only tested on glibc)
diff --git a/snooze.c b/snooze.c
index 60f7bff..3a5185d 100644
--- a/snooze.c
+++ b/snooze.c
@@ -230,6 +230,7 @@ int main(int argc, char *argv[])
 	int c;
 	time_t t;
 	time_t now = time(0);
+	time_t last = 0;
 
 	/* default: every day at 00:00:00 */
 	memset(weekday, '*', sizeof weekday);
@@ -348,6 +349,11 @@ int main(int argc, char *argv[])
 
 	while (!alarm_rang) {
 		now = time(0);
+		if (now < last) {
+			t = find_next(now);
+			if (vflag)
+				printf("Time moved backwards, rescheduled for %s\n", isotime(tm));
+		}
 		t = mktime(tm);
 		if (t <= now) {
 			if (now - t <= slack)  // still about time
@@ -365,6 +371,7 @@ int main(int argc, char *argv[])
 			struct timespec ts;
 			ts.tv_nsec = 0;
 			ts.tv_sec = t - now > SLEEP_PHASE ? SLEEP_PHASE : t - now;
+			last = now;
 			nanosleep(&ts, 0);
 			// we just iterate again when this exits early
 		}