time: Try to figure out some sensible timezone names from the TZ offset, and collect that from ip-api

apps/find-timezone.c

@@ -0,0 +1,34 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+#include <time.h>
+#include <unistd.h>
+#include <sys/time.h>
+#include <toaru/json.h>
+#include <toaru/hashmap.h>
+#include <toaru/list.h>
+
+typedef struct JSON_Value Value;
+
+#define LOCATION_DATA_PATH "/tmp/location-data.json"
+
+int main(int argc, char * argv[]) {
+	/* See if the location data already exists... */
+	char cmdline[1024];
+	Value * locationData = json_parse_file(LOCATION_DATA_PATH);
+	if (!locationData) {
+		sprintf(cmdline, "fetch -o \"" LOCATION_DATA_PATH "\" \"http://ip-api.com/json/?fields=lat,lon,city,offset\"");
+		system(cmdline);
+		locationData = json_parse_file(LOCATION_DATA_PATH);
+	}
+	/* If we still failed to load it, then bail. */
+	if (!locationData) {
+		return 1;
+	}
+	double offset = JSON_KEY(locationData, "offset")->number;
+
+	printf("%d\n", (int)offset);
+	return 0;
+}
+
+

apps/weather-tool.c

@@ -33,7 +33,7 @@ int main(int argc, char * argv[]) {
 		/* See if the location data already exists... */
 		Value * locationData = json_parse_file(LOCATION_DATA_PATH);
 		if (!locationData) {
-			sprintf(cmdline, "fetch -o \"" LOCATION_DATA_PATH "\" \"http://ip-api.com/json/?fields=lat,lon,city\"");
+			sprintf(cmdline, "fetch -o \"" LOCATION_DATA_PATH "\" \"http://ip-api.com/json/?fields=lat,lon,city,offset\"");
 			system(cmdline);
 			locationData = json_parse_file(LOCATION_DATA_PATH);
 		}

base/etc/startup.d/99_runstart.sh

@@ -6,9 +6,7 @@ export-cmd START kcmdline -g start
 export USER=root
 export HOME=/home/root
 
-export TZ=JST
-export TZ_OFFSET=32400
-
+export-cmd TZ_OFFSET find-timezone
 export-cmd GETTY_ARGS qemu-fwcfg opt/org.toaruos.gettyargs
 
 echo -n "Launching startup application..." > /dev/pex/splash

libc/time/localtime.c

@@ -122,12 +122,6 @@ static struct tm * fill_time(const time_t * timep, struct tm * _timevalue, const
 #define HOURS    3600
 #define MINUTES  60
 
-static char * get_timezone(void) {
-	char * tzEnv = getenv("TZ");
-	if (!tzEnv || strlen(tzEnv) != 3) return "UTC";
-	return tzEnv;
-}
-
 static int get_timezone_offset(void) {
 	char * tzOff = getenv("TZ_OFFSET");
 	if (!tzOff) return 0;
@@ -137,6 +131,47 @@ static int get_timezone_offset(void) {
 	return out;
 }
 
+struct timezone_offset_db {
+	int offset;
+	const char * abbrev;
+};
+
+static struct timezone_offset_db common_offsets[] = {
+	{0, "UTC"},
+	{1 * HOURS, "CEST"}, /* Central Europe Standard Time */
+	{8 * HOURS, "SST"}, /* Singapore Standard Time */
+	{9 * HOURS, "JST"}, /* Japan Standard Time */
+	{-5 * HOURS, "EST"}, /* US Eastern Standard */
+	{-6 * HOURS, "CST"}, /* US Central Standard */
+	{-7 * HOURS, "MST"}, /* US Mountain Standard */
+	{-8 * HOURS, "PST"}, /* US Pacific Standard */
+	{0, NULL},
+};
+
+static char * get_timezone(void) {
+	static char buf[20];
+	char * tzEnv = getenv("TZ");
+	if (!tzEnv) {
+		/* Is there an offset? */
+		int offset = get_timezone_offset();
+		for (struct timezone_offset_db * db = common_offsets; db->abbrev; db++) {
+			if (offset == db->offset) return (char*)db->abbrev;
+		}
+		/* Is it some number of hours? */
+		if (offset % HOURS == 0) {
+			if (offset > 0) {
+				snprintf(buf, 20, "UTC+%d", offset / HOURS);
+			} else {
+				snprintf(buf, 20, "UTC-%d", -offset / HOURS);
+			}
+			return buf;
+		}
+		return "???";
+	}
+	return tzEnv;
+}
+
+
 struct tm *localtime_r(const time_t *timep, struct tm * _timevalue) {
 	return fill_time(timep, _timevalue, get_timezone(), get_timezone_offset());
 }