initial commit of snooze

1 files changed, 333 insertions, 0 deletions

diff --git a/snooze.c b/snooze.c
new file mode 100644
index 0000000..ce6d93d
--- /dev/null
+++ b/snooze.c
@@ -0,0 +1,333 @@
+/*
+ * snooze - run a command at a particular time
+ *
+ * To the extent possible under law,
+ * Christian Neukirchen <chneukirchen@gmail.com>
+ * has waived all copyright and related or neighboring rights to this work.
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+/*
+##% gcc -Os -Wall -g -o $STEM $FILE -Wextra -Wwrite-strings
+*/
+
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#include <ctype.h>
+#include <errno.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include <unistd.h>
+
+#ifdef __linux__
+#include <sys/auxv.h>
+#endif
+
+static long slack = 60;
+#define SLEEP_PHASE 300
+static int nflag, vflag;
+
+static int timewait = 1;
+static int randdelay = 0;
+static char *timefile;
+
+static sig_atomic_t alarm_rang = 0;
+
+static void
+wakeup(int sig)
+{
+	(void)sig;
+	alarm_rang = 1;
+}
+
+static long
+parse_int(char **s, size_t minn, size_t maxn)
+{
+	long n;
+	char *end;
+
+	errno = 0;
+	n = strtol(*s, &end, 10);
+	if (errno) {
+		perror("strtol");
+		exit(1);
+	}
+	if (n < (long)minn || n >= (long)maxn) {
+		fprintf(stderr, "number outside %zd <= n < %zd\n", minn, maxn);
+		exit(1);
+	}
+	*s = end;
+	return n;
+}
+
+static int
+parse(char *expr, char *buf, long bufsiz, int offset)
+{
+	char *s;
+	long i, n = 0, n0 = 0;
+
+	memset(buf, ' ', bufsiz);
+
+	s = expr;
+	while (*s) {
+		switch (*s) {
+		case '0': case '1': case '2': case '3': case '4':
+                case '5': case '6': case '7': case '8': case '9':
+			n = parse_int(&s, -offset, bufsiz);
+			buf[n+offset] = '*';
+			break;
+		case '-':
+			n0 = n;
+			s++;
+			n = parse_int(&s, -offset, bufsiz);
+			for (i = n0; i <= n; i++)
+				buf[i+offset] = '*';
+			break;
+		case '/':
+			s++;
+			n0 = n;
+			n = parse_int(&s, -offset, bufsiz);
+			if (n == 0)  // / = *
+				n = 1;
+			for (i = n0; i < bufsiz; i += n)
+				buf[i+offset] = '*';
+			break;
+                case ',':
+			s++;
+			n = 0;
+			break;
+		case '*':
+			s++;
+			n = 0;
+			for (i = 0; i < bufsiz; i++)
+				buf[i+offset] = '*';
+			break;
+		default:
+			fprintf(stderr, "can't parse: %s %s\n", expr, s);
+			exit(1);
+		}
+	}
+
+	return 0;
+}
+
+char weekday[8] = {0};
+char dayofmonth[31] = {0};
+char month[12] = {0};
+char dayofyear[366] = {0};
+char weekofyear[53] = {0};
+char hour[24] = {0};
+char minute[60] = {0};
+char second[61] = {0};
+
+int
+isoweek(struct tm *tm)
+{
+	/* ugh, but easier than the correct formula... */
+	char weekstr[3];
+	char *w = weekstr;
+	strftime(weekstr, sizeof weekstr, "%V", tm);
+	return parse_int(&w, 1, 54);
+}
+
+time_t
+find_next(time_t from)
+{
+	time_t t;
+	struct tm *tm;
+
+	t = from;
+	tm = localtime(&t);
+
+next_day:
+	while (!(weekday[tm->tm_wday] == '*'
+	    && dayofmonth[tm->tm_mday-1] == '*'
+	    && month[tm->tm_mon] == '*'
+	    && weekofyear[isoweek(tm)] == '*'
+	    && dayofyear[tm->tm_yday] == '*')) {
+		if (month[tm->tm_mon] != '*') {
+			// if month is not good, step month
+			tm->tm_mon++;
+			tm->tm_mday = 1;
+		} else {
+			tm->tm_mday++;
+		}
+
+		tm->tm_sec = 0;
+		tm->tm_min = 0;
+		tm->tm_hour = 0;
+
+		t = mktime(tm);
+		if (t > from+(365*24*60*60))  // no result within a year
+			return -1;
+	}
+
+	int y = tm->tm_yday;  // save yday
+
+	while (!(hour[tm->tm_hour] == '*'
+	    && minute[tm->tm_min] == '*'
+	    && second[tm->tm_sec] == '*')) {
+		if (hour[tm->tm_hour] != '*') {
+			tm->tm_hour++;
+			tm->tm_min = 0;
+			tm->tm_sec = 0;
+		} else if (minute[tm->tm_min] != '*') {
+			tm->tm_min++;
+			tm->tm_sec = 0;
+		} else {
+			tm->tm_sec++;
+		}
+		t = mktime(tm);
+		if (tm->tm_yday != y)  // hit a different day, retry...
+			goto next_day;
+	}
+	    
+	return t;
+}
+
+static char isobuf[25];
+char *
+isotime(const struct tm *tm)
+{
+	strftime(isobuf, sizeof isobuf, "%FT%T%z", tm);
+	return isobuf;
+}
+
+int main(int argc, char *argv[])
+{
+	int c;
+	time_t now = time(0);
+
+	/* default: every day at 00:00:00 */
+	memset(weekday, '*', sizeof weekday);
+	memset(dayofmonth, '*', sizeof dayofmonth);
+	memset(month, '*', sizeof month);
+	memset(dayofyear, '*', sizeof dayofyear);
+	memset(weekofyear, '*', sizeof weekofyear);
+	hour[0] = '*';
+	minute[0] = '*';
+	second[0] = '*';
+
+	while ((c = getopt(argc, argv, "D:W:H:M:S:T:R:d:m:ns:t:vw:")) != -1)
+                switch(c) {
+		case 'D': parse(optarg, dayofyear, sizeof dayofyear, -1); break;
+		case 'W': parse(optarg, weekofyear, sizeof weekofyear, -1); break;
+		case 'H': parse(optarg, hour, sizeof hour, 0); break;
+		case 'M': parse(optarg, minute, sizeof minute, 0); break;
+		case 'S': parse(optarg, second, sizeof second, 0); break;
+		case 'd': parse(optarg, dayofmonth, sizeof dayofmonth, -1); break;
+		case 'm': parse(optarg, month, sizeof month, -1); break;
+		case 'w': parse(optarg, weekday, sizeof weekday, 0);
+			// special case: sunday is both 0 and 7.
+			if (weekday[7] == '*') 
+				weekday[0] = '*';
+			break;
+		case 'n': nflag++; break;
+		case 'v': vflag++; break;
+		case 's': slack = atoi(optarg); break;
+		case 'T': timewait = atoi(optarg); break;
+		case 't': timefile = optarg; break;
+		case 'R': randdelay = atoi(optarg); break;
+		default:
+                        fprintf(stderr, "Usage: %s [-nv] [-t timefile] [-T timewait] [-R randdelay] [-s slack]\n"
+			    "  [-d mday] [-m mon] [-w wday] [-D yday] [-W yweek] [-H hour] [-M min] [-S sec] COMMAND...\n"
+			    "Timespec: exact: 1,3,5\n"
+			    "          range: 1-7\n"
+			    "          every n-th: /10\n", argv[0]);
+                        exit(2);
+                }
+
+	time_t start = now + 1;
+
+	if (timefile) {
+		struct stat st;
+		if (stat(timefile, &st) < 0) {
+			if (errno != ENOENT)
+				perror("stat");
+		} else {
+			if (st.st_mtime + timewait > start)
+				start = st.st_mtime + timewait;
+		}
+	}
+
+	if (randdelay) {
+		long delay;
+#ifdef __linux__
+		long rnd = getauxval(AT_RANDOM);
+		if (rnd > 0)
+			delay = rnd % randdelay;
+		else
+#endif
+		{
+			srand48(getpid() ^ start);
+			delay = lrand48() % randdelay;
+		}
+		if (vflag)
+			printf("randomly delaying by %lds.\n", delay);
+		start += delay;
+	}
+
+	time_t t = find_next(start);
+	if (t < 0) {
+		fprintf(stderr, "no satisfying date found within a year.\n");
+		exit(2);
+	}
+
+	if (nflag) {
+		/* dry-run, just output the next 5 dates. */
+		int i;
+		for (i = 0; i < 5; i++) {
+			if (t > 0)
+				printf("%s\n", isotime(localtime(&t)));
+			t = find_next(t + 1);
+		}
+		exit(0);
+	}
+
+	struct tm *tm = localtime(&t);
+	if (vflag)
+		printf("Snoozing until %s\n", isotime(tm));
+
+	// setup SIGALRM handler to force early execution
+	struct sigaction sa;
+	sa.sa_handler = &wakeup;
+	sa.sa_flags = SA_RESTART;
+	sigfillset(&sa.sa_mask);
+	sigaction(SIGALRM, &sa, NULL);  // XXX error handling
+
+	while (!alarm_rang) {
+		now = time(0);
+		t = mktime(tm);
+		if (t <= now) {
+			if (now - t <= slack)  // still about time
+				break;
+			else {  // reschedule to next event
+				if (vflag)
+					printf("Missed execution at %s\n", isobuf);
+				t = find_next(now + 1);
+				tm = localtime(&t);
+				if (vflag)
+					printf("Snoozing until %s\n", isotime(tm));
+			}
+		} else {
+			// do some sleeping, but not more than SLEEP_PHASE
+			struct timespec ts;
+			ts.tv_nsec = 0;
+			ts.tv_sec = t - now > SLEEP_PHASE ? SLEEP_PHASE : t - now;
+			nanosleep(&ts, 0);
+			// we just iterate again when this exits early
+		}
+	}
+
+	// no command to run, the outside script can go on
+	if (argc == optind)
+		return 0;
+
+	execvp(argv[optind], argv+optind);
+	perror("execvp");
+	return 255;
+}