Add per-second scheduling into the cron(8). Right now it's

only available via the new @every_second shortcut. ENOTIME to
implement crontab(5) format extensions to allow more flexible
scheduling.

In order to address some concerns expressed by Terry Lambert
while discussing the topic few years ago, about per-second cron
possibly causing some bad effects on /etc/crontab by stat()ing
it every second instead of every minute now (i.e. atime update),
only check that database needs to be reloaded on every 60-th
loop run. This should be close enough to the current behaviour.

Add "@every_minute" shortcut while I am here.

MFC after:	1 month

4 files changed, 45 insertions, 9 deletions

diff --git a/usr.sbin/cron/cron/cron.c b/usr.sbin/cron/cron/cron.c
index 8524ff9dfcb8..011458a537f1 100644
--- a/usr.sbin/cron/cron/cron.c
+++ b/usr.sbin/cron/cron/cron.c
@@ -98,6 +98,7 @@ main(argc, argv)
 	char	*argv[];
 {
 	cron_db	database;
+	int runnum;
 
 	ProgramName = argv[0];
 
@@ -149,21 +150,24 @@ main(argc, argv)
 	load_database(&database);
 	run_reboot_jobs(&database);
 	cron_sync();
+	runnum = 0;
 	while (TRUE) {
 # if DEBUGGING
 	    /* if (!(DebugFlags & DTEST)) */
 # endif /*DEBUGGING*/
 			cron_sleep(&database);
 
-		load_database(&database);
+		if (runnum % 60 == 0)
+			load_database(&database);
 
 		/* do this iteration
 		 */
 		cron_tick(&database);
 
-		/* sleep 1 minute
+		/* sleep 1 second
 		 */
-		TargetTime += 60;
+		TargetTime += 1;
+		runnum += 1;
 	}
 }
 
@@ -194,22 +198,23 @@ cron_tick(db)
 	static time_t	diff = 0, /* time difference in seconds from the last offset change */
 		difflimit = 0; /* end point for the time zone correction */
 	struct tm	otztm; /* time in the old time zone */
-	int		otzminute, otzhour, otzdom, otzmonth, otzdow;
+	int		otzsecond, otzminute, otzhour, otzdom, otzmonth, otzdow;
  	register struct tm	*tm = localtime(&TargetTime);
-	register int		minute, hour, dom, month, dow;
+	register int		second, minute, hour, dom, month, dow;
 	register user		*u;
 	register entry		*e;
 
 	/* make 0-based values out of these so we can use them as indicies
 	 */
+	second = tm->tm_sec -FIRST_SECOND;
 	minute = tm->tm_min -FIRST_MINUTE;
 	hour = tm->tm_hour -FIRST_HOUR;
 	dom = tm->tm_mday -FIRST_DOM;
 	month = tm->tm_mon +1 /* 0..11 -> 1..12 */ -FIRST_MONTH;
 	dow = tm->tm_wday -FIRST_DOW;
 
-	Debug(DSCH, ("[%d] tick(%d,%d,%d,%d,%d)\n",
-		getpid(), minute, hour, dom, month, dow))
+	Debug(DSCH, ("[%d] tick(%d,%d,%d,%d,%d,%d)\n",
+		getpid(), second, minute, hour, dom, month, dow))
 
 	if (dst_enabled && last_time != 0 
 	&& TargetTime > last_time /* exclude stepping back */
@@ -262,6 +267,7 @@ cron_tick(db)
 
 			/* make 0-based values out of these so we can use them as indicies
 			 */
+			otzsecond = otztm.tm_sec -FIRST_SECOND;
 			otzminute = otztm.tm_min -FIRST_MINUTE;
 			otzhour = otztm.tm_hour -FIRST_HOUR;
 			otzdom = otztm.tm_mday -FIRST_DOM;
@@ -283,7 +289,8 @@ cron_tick(db)
 					  e->uid, e->gid, e->cmd))
 
 			if ( diff != 0 && (e->flags & (RUN_AT|NOT_UNTIL)) ) {
-				if (bit_test(e->minute, otzminute)
+				if (bit_test(e->second, otzsecond)
+				 && bit_test(e->minute, otzminute)
 				 && bit_test(e->hour, otzhour)
 				 && bit_test(e->month, otzmonth)
 				 && ( ((e->flags & DOM_STAR) || (e->flags & DOW_STAR))
@@ -302,7 +309,8 @@ cron_tick(db)
 					continue;
 			}
 
-			if (bit_test(e->minute, minute)
+			if (bit_test(e->second, second)
+			 && bit_test(e->minute, minute)
 			 && bit_test(e->hour, hour)
 			 && bit_test(e->month, month)
 			 && ( ((e->flags & DOM_STAR) || (e->flags & DOW_STAR))
diff --git a/usr.sbin/cron/cron/cron.h b/usr.sbin/cron/cron/cron.h
index 38eb33b0c6f5..387c72bbed09 100644
--- a/usr.sbin/cron/cron/cron.h
+++ b/usr.sbin/cron/cron/cron.h
@@ -124,6 +124,10 @@
 			 LineNumber = ln; \
 			}
 
+#define	FIRST_SECOND	0
+#define	LAST_SECOND	59
+#define	SECOND_COUNT	(LAST_SECOND - FIRST_SECOND + 1)
+
 #define	FIRST_MINUTE	0
 #define	LAST_MINUTE	59
 #define	MINUTE_COUNT	(LAST_MINUTE - FIRST_MINUTE + 1)
@@ -165,6 +169,7 @@ typedef	struct _entry {
 #endif
 	char		**envp;
 	char		*cmd;
+	bitstr_t	bit_decl(second, SECOND_COUNT);
 	bitstr_t	bit_decl(minute, MINUTE_COUNT);
 	bitstr_t	bit_decl(hour,   HOUR_COUNT);
 	bitstr_t	bit_decl(dom,    DOM_COUNT);
diff --git a/usr.sbin/cron/crontab/crontab.5 b/usr.sbin/cron/crontab/crontab.5
index 458175e7a48d..9be37df264e5 100644
--- a/usr.sbin/cron/crontab/crontab.5
+++ b/usr.sbin/cron/crontab/crontab.5
@@ -232,6 +232,8 @@ string		meaning
 @daily		Run once a day, "0 0 * * *".
 @midnight	(same as @daily)
 @hourly		Run once an hour, "0 * * * *".
+@every_minute	Run once a minute, "*/1 * * * *".
+@every_second	Run once a second.
 .Ed
 .Sh EXAMPLE CRON FILE
 .Bd -literal
diff --git a/usr.sbin/cron/lib/entry.c b/usr.sbin/cron/lib/entry.c
index ea015da62704..9c1106a3d735 100644
--- a/usr.sbin/cron/lib/entry.c
+++ b/usr.sbin/cron/lib/entry.c
@@ -151,6 +151,7 @@ load_entry(file, error_func, pw, envp)
 			e->flags |= WHEN_REBOOT;
 		} else if (!strcmp("yearly", cmd) || !strcmp("annually", cmd)){
 			Debug(DPARS, ("load_entry()...yearly shortcut\n"))
+			bit_set(e->second, 0);
 			bit_set(e->minute, 0);
 			bit_set(e->hour, 0);
 			bit_set(e->dom, 0);
@@ -159,6 +160,7 @@ load_entry(file, error_func, pw, envp)
 			e->flags |= DOW_STAR;
 		} else if (!strcmp("monthly", cmd)) {
 			Debug(DPARS, ("load_entry()...monthly shortcut\n"))
+			bit_set(e->second, 0);
 			bit_set(e->minute, 0);
 			bit_set(e->hour, 0);
 			bit_set(e->dom, 0);
@@ -167,6 +169,7 @@ load_entry(file, error_func, pw, envp)
 			e->flags |= DOW_STAR;
 		} else if (!strcmp("weekly", cmd)) {
 			Debug(DPARS, ("load_entry()...weekly shortcut\n"))
+			bit_set(e->second, 0);
 			bit_set(e->minute, 0);
 			bit_set(e->hour, 0);
 			bit_nset(e->dom, 0, (LAST_DOM-FIRST_DOM+1));
@@ -175,6 +178,7 @@ load_entry(file, error_func, pw, envp)
 			bit_set(e->dow, 0);
 		} else if (!strcmp("daily", cmd) || !strcmp("midnight", cmd)) {
 			Debug(DPARS, ("load_entry()...daily shortcut\n"))
+			bit_set(e->second, 0);
 			bit_set(e->minute, 0);
 			bit_set(e->hour, 0);
 			bit_nset(e->dom, 0, (LAST_DOM-FIRST_DOM+1));
@@ -182,11 +186,28 @@ load_entry(file, error_func, pw, envp)
 			bit_nset(e->dow, 0, (LAST_DOW-FIRST_DOW+1));
 		} else if (!strcmp("hourly", cmd)) {
 			Debug(DPARS, ("load_entry()...hourly shortcut\n"))
+			bit_set(e->second, 0);
 			bit_set(e->minute, 0);
 			bit_nset(e->hour, 0, (LAST_HOUR-FIRST_HOUR+1));
 			bit_nset(e->dom, 0, (LAST_DOM-FIRST_DOM+1));
 			bit_nset(e->month, 0, (LAST_MONTH-FIRST_MONTH+1));
 			bit_nset(e->dow, 0, (LAST_DOW-FIRST_DOW+1));
+		} else if (!strcmp("every_minute", cmd)) {
+			Debug(DPARS, ("load_entry()...every_minute shortcut\n"))
+			bit_set(e->second, 0);
+			bit_nset(e->minute, 0, (LAST_MINUTE-FIRST_MINUTE+1));
+			bit_nset(e->hour, 0, (LAST_HOUR-FIRST_HOUR+1));
+			bit_nset(e->dom, 0, (LAST_DOM-FIRST_DOM+1));
+			bit_nset(e->month, 0, (LAST_MONTH-FIRST_MONTH+1));
+			bit_nset(e->dow, 0, (LAST_DOW-FIRST_DOW+1));
+		} else if (!strcmp("every_second", cmd)) {
+			Debug(DPARS, ("load_entry()...every_second shortcut\n"))
+			bit_nset(e->second, 0, (LAST_SECOND-FIRST_SECOND+1));
+			bit_nset(e->minute, 0, (LAST_MINUTE-FIRST_MINUTE+1));
+			bit_nset(e->hour, 0, (LAST_HOUR-FIRST_HOUR+1));
+			bit_nset(e->dom, 0, (LAST_DOM-FIRST_DOM+1));
+			bit_nset(e->month, 0, (LAST_MONTH-FIRST_MONTH+1));
+			bit_nset(e->dow, 0, (LAST_DOW-FIRST_DOW+1));
 		} else {
 			ecode = e_timespec;
 			goto eof;