Add simple cron implementation

Signed-off-by: David Oberhollenzer <david.oberhollenzer@tele2.at>

1 files changed, 139 insertions, 0 deletions

diff --git a/crond/main.c b/crond/main.c
new file mode 100644
index 0000000..d7cc33e
--- /dev/null
+++ b/crond/main.c
@@ -0,0 +1,139 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * Copyright (C) 2018 - David Oberhollenzer
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+#include "gcrond.h"
+
+static crontab_t *jobs;
+static sig_atomic_t run = 1;
+static sig_atomic_t rescan = 1;
+
+static void read_config(void)
+{
+	if (cronscan(GCRONDIR, &jobs)) {
+		fputs("Error reading configuration. Continuing anyway.\n",
+		      stderr);
+	}
+}
+
+static void cleanup_config(void)
+{
+	crontab_t *t;
+
+	while (jobs != NULL) {
+		t = jobs;
+		jobs = jobs->next;
+		delcron(t);
+	}
+}
+
+static int calc_timeout(void)
+{
+	time_t now = time(NULL), future;
+	struct tm tmstruct;
+	crontab_t mask, *t;
+	int minutes;
+
+	for (minutes = 0; minutes < 120; ++minutes) {
+		future = now + minutes * 60;
+
+		localtime_r(&future, &tmstruct);
+		cron_tm_to_mask(&mask, &tmstruct);
+
+		for (t = jobs; t != NULL; t = t->next) {
+			if (cron_should_run(t, &mask))
+				goto out;
+		}
+	}
+out:
+	return minutes ? minutes * 60 : 60;
+}
+
+static void runjobs(void)
+{
+	time_t now = time(NULL);
+	struct tm tmstruct;
+	crontab_t mask, *t;
+
+	localtime_r(&now, &tmstruct);
+	cron_tm_to_mask(&mask, &tmstruct);
+
+	for (t = jobs; t != NULL; t = t->next) {
+		if (cron_should_run(t, &mask))
+			runjob(t);
+	}
+}
+
+static void sighandler(int signo)
+{
+	switch (signo) {
+	case SIGINT:
+	case SIGTERM:
+		run = 0;
+		break;
+	case SIGHUP:
+		rescan = 1;
+		break;
+	}
+}
+
+int main(void)
+{
+	struct timespec stime;
+	struct sigaction act;
+	crontab_t *t;
+	int timeout;
+	pid_t pid;
+
+	memset(&act, 0, sizeof(act));
+	act.sa_handler = sighandler;
+	sigaction(SIGINT, &act, NULL);
+	sigaction(SIGTERM, &act, NULL);
+	sigaction(SIGHUP, &act, NULL);
+
+	while (run) {
+		if (rescan == 1) {
+			cleanup_config();
+			read_config();
+			timeout = 60;
+			rescan = 0;
+		} else {
+			runjobs();
+			timeout = calc_timeout();
+		}
+
+		stime.tv_sec = timeout;
+		stime.tv_nsec = 0;
+
+		while (nanosleep(&stime, &stime) != 0 && run && !rescan) {
+			if (errno != EINTR) {
+				perror("nanosleep");
+				break;
+			}
+		}
+
+		while ((pid = waitpid(-1, NULL, WNOHANG)) != -1) {
+			for (t = jobs; t != NULL; t = t->next) {
+				if (t->pid == pid) {
+					t->pid = -1;
+					break;
+				}
+			}
+		}
+	}
+
+	return EXIT_SUCCESS;
+}